Ever since I first started this tradition of posting holiday shortbread recipes, I've been struck by how just how quickly the season sneaks up on me. For better or worse, my self-imposed cookie publishing deadline never fails to call attention to how quickly the year's end is creeping up.  And 2022, well, it's been a creeper.

Funny enough, I actually had the idea for this recipe all ready to go last year, so I figured I'd be able to get this one done well in advance.  Let's all roll our eyes together on that one, shall we?  I should have known that simply having a great holiday cookie idea wasn't going to get me to make it any earlier.  I might aspire to proactivity, but I generally prefer to settle for procrastination.

But we're here now, and the cookies are baked, and they are very Christmas-y, and all is well.  They've got the aromatic spice-rich flavour of scratch-made gingerbread, and the buttery sweetness of shortbread.  I wish they had a better name than 'gingerbread shortbread' though... two breads in one name. Perhaps gingortbread? Shortgerbread? Maybe we need to mine other languages for some ideas.  The French sablé d'épices sounds pretty fancy.  Perhaps German - pfefferbutterkeks.  I kinda like that one.  I'll let you decide.

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Now then, if you just wanted to jump right on down to the recipe and get baking - well you go ahead and do that!  But I can't help reflect on the end of the year, and on why exactly it is that I'm here.  I create these recipes because I love food, AND because I love the wonderful, creative, educational doors that are opened up by food.  So, as I prepped the many gingerbread spices, I decided to write a little about the incredible and surprising chemistry of gingerbread.

Is it important that you understand the chemistry of gingerbread? Well... no? Yes? I don't know really - you can make these cookies without reading any of that stuff and they'll taste every bit as good as mine.  But spices and their unique chemical compositions have captured our imaginations - and our money - for centuries.  Intense and bloody wars have been fought for spices. Past and present global politics are intricately tied to the imperialist economies of the spice trade.  For better and for worse, the world has been shaped in part because of the unmistakable appeal of a cinnamon stick.  Spices matter, and they always have.

From a more pragmatic perspective, understanding the chemistry of spices can also make you a better cook.  No spice is defined by a single chemical.  Instead, spices are unique and distinctive thanks to the complex co-mingling of numerous complimentary organic compounds.  Many potent and distinctive compounds are actually found across a wide range of related and unrelated herbs and spices, albeit at different combinations and in the company of various compatriot compounds that affect our perception of the ingredients as a whole.  Eugenol, which I'll discuss below in more detail, is the key aroma/flavour component of cloves - but it's also found in cinnamon, nutmeg, ginger, sweet basil and... celery.  Yes, celery.

This isn't mere trivia though; a deeper understanding of food chemistry can change how you cook, and what flavours you bring together in your own culinary creations.  And really, that's why I'm here. I want you to cook, and to bake, and to experience food more deeply.  I want you to love what you do, to love your food, and to love learning.

Gingerbread is actually a very broad, very complex, and very old culinary tradition with a pretty wide array of types and subtypes.  Regardless of the variation, gingerbread is a pretty remarkable exercise in culinary extravagance - at least by the standards of the 16th-19th centuries.  Cookies would already be something of an extravagancy for Western bakers, but then imagine adding ginger, cinnamon, cloves, and nutmeg, all of which were sourced and shipped from from unfamiliar tropical lands located halfway across the world. Honestly, it's a little stunning to me that global economics have led us to think of most of these spices as everyday items.

Why do these spices captivate us so? Why did we spend outlandish quantities of money just to treat ourselves with them? Why did we fight and kill and die for them?

Chemistry.  Spices are loaded with intense, aromatic chemical compounds.  These contribute distinct and highly appealing scent and flavour profiles, combining in myriad ways to create the unique culinary signatures of the spices we enjoy  Because a little spice goes a long way, and because many of these compounds withstand cooking and baking relatively unscathed, they can have an outsized impact on the way we cook and bake.

But why do these spice compounds appeal to us? Why do we smell the bark of a cinnamon tree and instantly feel the desire to incorporate it into our food? Well, it's a little complicated.  Spices don't provide us with any meaningful nutrition, but they may actually help keep us alive in another way.  Many of the chemicals that draw us to spices also have antibacterial, antifungal, and/or other medicinal properties.  Spicing our food may have actually made it safer to eat.

Still, this is by no means the whole story.  Humans first started cooking food between 300,000 and 2 million years ago, but we most likely already had built-in tastes for aromatic spices.  But why would this be? One thought is that our distant evolutionary forebears developed positive associations with these ingredients thanks to the reproductive advantages conferred by self-medicating with them.  We see many different animals self-medicate with plants that they would otherwise avoid, ostensibly to treat things like digestive disorders and parasitic infections.  Plants produce chemicals meant to deter predation, including many distinctive and pungent ones that are meant to serve as flagrant warnings to any would-be plant-munchers.  But many animals have learned to co-opt these defensive compounds for their own benefits.  A chemical that keeps bacteria out of a plant may well also keep bacteria from running rampant in our bodies.  Any genetic variations that would have caused these animal ancestors to actually enjoy these compounds would most likely have conferred a further advantage.  A spoonful of sugar to help the medicine go down, if you will.

An evolutionarily driven penchant for medicinal compounds does make sense. But there's another interesting possibility too; we may like certain spices simply thanks to accidents of chemistry.  Chemistry - and especially organic chemistry (the branch of the science that concerns itself with carbon-containing molecules), is a fascinatingly structural thing.  We are able to detect and (in many cases) react to biologically important chemical compounds because of their shapes.

Let's look at simple table sugar, or sucrose.  Sucrose tastes sweet because of the way that molecules of it fit into tiny molecular receptors on our tongues, much like little locks and keys.  Contrast this with the chemical sucralose (sold under the brand name Splenda).  Sucralose does not exist in nature, so we certainly could not have evolved a liking for it.  But thanks to its shape and composition (and some other interesting stuff we're still working out), a molecule of sucralose interacts with those same receptors in a way that causes our brains to perceive it as 400-800 times sweeter than sugar.

Many of the organic compounds found in herbs and spices are chemically and structurally similar.  And while it is highly likely that we've evolved a taste for some of these thanks to their pharmaceutical benefits, it's also possible that other compounds simply came along for the ride.  Take a look at the chemical structures on the cookies below (yes, on the cookies).  You'll see that they all contain a hexagon.  These hexagons are rings made up of six carbon atoms (one at each corner).  Three of these hexagons have an additional set of three lines drawn in an alternating fashion around the inside.  This is the structural drawing for benzene (C₆H₆).  Benzene is an incredibly important building block for a vast array of organic molecules.  But on its own, benzene is, uh... not great for you.  It's a known carcinogen, and exposure to large quantities can be fatal.  But it also has a strange, semi-sweet smell that can be strangely appealing.  In fact, you've probably smelled it pretty recently; benzene is partly responsible for the distinctive scent of gasoline.

It's at this point that I should note that there's really no such thing as a 'good' or a 'bad' chemical.  An appealing chemical compound that may have helped our ancestors treat or avoid illness can still present risks, or even outright danger.  The chemicals I've (literally) outlined below are responsible for making gingerbread special, and yet each one is definitely complex from the perspective of health and safety.

Learning about this stuff can be eye-opening, but also a little nerve-wracking.  It's worth remembering that quantities are very, very meaningful when it comes to chemistry and our health.  As Paracelsus so famously said, the dose makes the poison. Take Vitamin A, for example.  It's necessary for our survival, and yet large doses of it can destroy your liver and even kill you.  Because it's not a binary, black-and-white sort of thing, the mere presence of any one chemical compound in your food doesn't necessarily mean all that much.  Just because chemical 'X' is in your dinner doesn't mean that it's going to cure all that ails you, nor does it immediately put you at risk for dropping dead.  This grey area can be frustrating, but it can also be fascinating.  Tasty, too.

Gingerbread is a positive cavalcade of incredible and intense spices.  You can buy gingerbread mixes, but making your own spice blend really makes you realize just how many really amazing flavours and aromas are coming together just so we can make cookies.  To celebrate that fact, I thought it'd be fun to explore a handful of the fascinating chemicals that make gingerbreads (and its individual component spices) so special.

Below you'll find what I think are some of the most interesting flavour-building chemicals found in gingerbread shortbread.  I've included a little science and story with each one, and I've illustrated the chemical structures with royal icing on the cookies.  Why did I do this? Three reasons. First, I really like organic chemistry structural drawings.  Second, I had initially tried drawing mathematically accurate snowflakes, and I was not having a good time.  So you get a chemistry article instead of a math one.  Third - there are a lot of food blogs out there in the world, and it can be difficult at times to feel like you're doing something truly novel.  But I'm going to go out on a limb and guess that I'm the first food writer to bake hybrid gingerbread-shortbread cookies and ice them with the chemical structure of a psychoactive spice.  That's my Christmas present to me.

(FYI, it's not vital that you understand how these drawings work in order to understand the writing, but if you're unfamiliar with chemistry structural notation and you want to learn what exactly these funky little geometric drawings represent, give this link a try.  It does take a bit of time to learn, but it's actually quite beautifully intuitive once you get the basics down.)

Fun to say, and fun to eat. Zingiberene is a distinctive and dominant flavour component of ginger (Zingiber officinale).  It is, safe to say, pretty important to gingerbread.  But while it is responsible for much of the flavour of ginger, it's not responsible for the spicy 'bite' that you get from raw ginger.  That honour belongs to a compound called gingerol, which activates the spice receptors found on our tongues and other mucous membranes in a fashion similar to the capsaicin found in chilies.

Interestingly, while zingiberene survives the drying process nicely, gingerol does not.  The dried ginger you use to make gingerbread contains plenty of ginger flavour, but the gingerol actually breaks down into other chemicals called shogaols.  But if you've ever tasted dried ginger, you'll know that it's also quite fiery. That's because shogaols are actually even more pungent/spicy than gingerol, making dried ginger even more fiery than its fresh compatriot.  But why then, is gingerbread not a fiery exercise in cookie masochism? Well, gingerols and shogaols begin to break down when they're heated.  Zingiberene, on the other hand, makes it through the baking process relatively unscathed, leaving your cookies with plenty of ginger flavour, and little of that ginger fire.

Dried ginger is noticeably different from fresh ginger, and is in some respects more similar to cooked ginger.  This is thanks in part to the presence of zingerone, which is formed from the breakdown of gingerol.  Zingerone gives dried and cooked ginger a distinctive sweetness not found in the raw root.  It's also, interestingly, very chemically similar to vanillin (the primary scent component of vanilla) and eugenol, which we'll see below in a moment.

Ginger has long been treated as both a food and a medicine.  Zingiberene and other ginger constituents have a lot of promising and potentially beneficial effects (especially vis a vis nausea and digestion), but it's quite a bit too much to get into the details here.  If you're interested in learning more, Science Direct is a good jumping off point.

This probably isn't going to surprise you, but cinnamaldehyde is an aldehyde found in cinnamon.

Cinnamaldehyde is one of many highly fragrant and distinctive food aldehydes. Vanillin (in vanilla) and benzaldehyde (in almonds) are two other prominent ones that frequently find their way into baked goods.  Interestingly, it's the aldehydes decanal and dodecanal in cilantro that give it the distinctive flavour and the 'soapy' quality that some people despise.  How you perceive those particular aldehydes depends on your genetics.

Cinnamaldehyde is the key component responsible for the distinct aroma of cinnamon and cassia.  It's also one of those chemicals compounds that happens to have a fascinating, almost bizarre diversity of uses.  Cinnamaldehyde is a pretty solid anti-mosquito insecticide, displays interesting anti-mutagenic and DNA protective properties, and can be used to prevent steel from corroding.

So it's good for you, right? Well... sort of?  You see, cinnamaldehyde also decomposes to form styrene, which is a known carcinogen.  All cinnamon contains at least a little styrene (more if its shipped and/or stored under poor conditions), and the potential danger posed by consuming extremely high levels of cinnamon can't be ruled out.  Do the quantities of cinnamon used in baking present any risks? Almost certainly no. But, by the same logic, it's not fair to say that it will confer some kind of health or protective benefit either.  Dosage is, as always, a complex thing to sort out.

Fortunately, cinnamaldehyde smells incredible, and it makes gingerbread shortbread (and so many other things) taste amazing.  So regardless of what else it does, you'll always have that.

Alpha-terpineol is a bit of an odd inclusion in this list, as its not a chemical whose aroma immediately jumps to mind when you think about gingerbread.  One of four possible isomers of terpineol, α-terpineol is frequently described as having a floral/lilac aroma, with sweet, woody, and citrusy notes.  It comes into play in this recipe for gingerbread shortbread thanks to the use of cardamom.

Cardamom is a highly complex, and (in my opinion) underrated spice.  It's sweet, citrusy, piney, and floral all at once.  This has a lot to do with its complex organic chemistry, and the many different chemicals that contribute flavour and aroma.  Alpha-terpineol is only one of these chemicals, but it serves as a really lovely counterpoint to the headier and more pungent gingerbread flavours that you find in spices like cinnamon, nutmeg, and cloves.

As with many of the other compounds listed here, α-terpineol has an impressive list of capabilities and potential uses.  But what I find particularly interesting about α-terpineol is how structurally similar it is to a number of other very distinctive and very important flavour chemicals.  A wide variety of natural and laboratory processes can be used to convert α-terpineol to or from α-pinene (responsible for the evergreen scent of pines and rosemary) and limonene (responsible for the distinctive aroma of citrus peels), all with relative ease.  In fact, cardamom contains all of these closely related compounds and many more, which helps explain why it's so complex, yet broadly complimentary.  If you haven't used cardamom much in the past, I highly encourage you to explore with it more now, as the chemistry makes it something of a culinary secret weapon.

A little numbness while reading about gingerbread could be explained by my waxing poetic about organic chemistry.  A little numbness while eating gingerbread, on the other hand, could be caused by eugenol.

Eugenol is difficult to describe, mainly because we can only really use self-referential terms.  Cloves are loaded with eugenol, and it's the primary source of their unique and powerful spiced aroma.  We can basically say that eugenol smells like cloves, and vice versa.  However, cloves aren't the only source of eugenol - even in this shortbread recipe!  Bay leaves (which I used in last year's shortbread), nutmeg, cinnamon, and basil also contain significant quantities of eugenol, albeit at levels that tend to compliment rather than define their fundamental aromas.

But eugenol isn't just a flavour - it's also an anesthetic and analgesic.  It's commonly used in dentistry, and - interestingly - for anesthetizing or even euthanizing fish. Good to know, if you have to put a fish to sleep.  Eugenol's anesthetic properties aren't especially powerful in mammals, and the compound seems to be toxic to the liver at particularly high doses or with prolonged exposure, so it's not a great candidate for systemic anesthetic use in humans.  However, scientific investigation and understanding of the anesthetic properties of eugenol led to the development of chemically similar and highly potent anesthetics such as propofol.

In food, moderate levels of eugenol can cause a numbness or tingling on the tongue.  Clove-containing foods like gingerbread can induce this sensation in some people, but cloves aren't the only culprits. Interestingly, celery - which contains surprisingly high levels of eugenol - makes some people's tongues particularly numb or tingly.

If you like controversial and complicated chemicals, then you'll find that I've saved the best for last.

Myristicin is a key flavour and aroma component in nutmeg, and ohhhh boy is it interesting stuff.  It's an effective insecticide, and a synergistic one at that, meaning that it actually improves the efficacy of other insecticides.  It's also toxic to living cells, yet potentially useful for mitigating the toxic effects of chemotherapy. But there's another feature of myristicin that tends to garner the most pop-sci attention: it gets you high.

Before I go any further, let me say right off the bat that a) eating a little nutmeg isn't going to get you high, and b) basically nobody (myself included) would EVER recommend you try to get high with nutmeg.  You will not have a good time.

Myristicin has a chemical structure that is very similar to the class of drugs known as amphetamines.  It can serve as a starting point for the synthetic production of designer psychedelic drugs like MMDA and MDMA (ecstasy).  But even on its own myristicin has psychoactive properties, including hallucinogenic effects.  But as a recreational drug, nutmeg leaves a great deal to be desired.  Consumption of large quantities of nutmeg can cause convulsions, palpitations, nausea, and other rather unpleasant effects.  On top of this, the effects of nutmeg toxicity can last for many hours, or even days at a time.  The overall mechanism is not terribly well understood, and nutmeg toxicity seems to vary a great deal between individuals.  Myristicin itself is probably responsible for some of aspects of nutmeg toxicity, but the many other compounds present (including eugenol - see above) likely play a role as well.

So... should you worry about cooking with nutmeg? No - unless you're planning on using really, really ridiculous quantities of it.  An individual dose of 15 grams of nutmeg (around 7 tsp) will deliver a 400 mg dose of myristicin - enough to induce "mild cerebral stimulation" in 4 out of 10 adult subjects - though in some cases 5 grams (around 2.3 tsp) is enough.  But the toxic effects of nutmeg begin to kick in at around 5 grams, meaning that most people consuming large quantities of nutmeg will feel either sick and high, or just plain sick.

Interestingly, it is possible to accidentally overdose on nutmeg.  Most nutmeg overdoses/poisonings are due to intentional recreational ingestion, but a over a quarter of reported poisonings are caused by people (especially children) getting large amounts of powdered nutmeg on their skin, in their eyes, or on their mucous membranes.  If you grind (rather than grate) nutmeg yourself, especially with an electric spice grinder, make sure to let it settle so you don't get a face full of nutmeg dust.