Preheat the oven to 350 F.

Whisk together the oil and flour in a large, heavy cast-iron pot or very deep frying pan. The mixture will be quite thick, but you should still be able to get all of the flour soaked into the oil.

Place the cast iron pot/pan in the oven and bake uncovered for 1-1.5 hours, stirring 2-3 times during this process. The roux is finished when it reaches a deep, reddish brown colour, not unlike an old penny.

While the roux is cooking, clean the crab thoroughly, and steam it using about 1 liter of water. A 900 g (2 lb) crab will need to be steamed for 15 minutes. If scaling up or down, use 7-8 minutes per 450 g (1 lb).

Skim and scum or debris from the water used to steam the crab. You will use this steaming water as a stock for the gumbo. Add enough water to make 2 liters, and set aside.

Crack the crab and pick out all the meat.

Dice the onion, golden beets, and kale stems and set aside. Coarsely chop the kale leaves and keep them separate from the other vegetables.

Peel and coarsely dice the Jerusalem artichokes. Add the chopped tubers to a small bowl of water with some vinegar or lemon juice to prevent browning. Set aside.

Peel, seed, and cut the butternut squash into 1 cm (~1/2 inch) cubes. Set aside.

Once the roux is cooked, remove it from the oven and transfer it to the stove top and heat on medium. Add the onion, kale stems, and beets. Stir together and cook for 2-3 minutes, taking care not to burn the roux. Add the garlic and cook for 5 minutes more.

(Note: if you've used a shallow pan, you'll have to transfer the roux-vegetable combination to a deeper pot at this point) Add the sage, bay leaf, and a pinch of salt and pepper to the roux. Slowly begin adding the crab broth a little at a time, whisking to combine with the roux. Once all of the broth has been added, reduce the heat to low.

Add the sausage, Jerusalem artichoke, and squash, cover and simmer for 30-40 minutes, or until the squash is tender.

Remove from heat and stir in the crab meat and the kale. Cover and allow to sit, away for 5-10 minutes. Serve as is, or over cooked long grain white rice.