Chapter four of the duck project doesn’t break any new culinary ground, but rather affirms that 1) confit is an excellent preparation for duck legs and 2) sous vide vastly simplifies this process. Duck confit is a specialty of Gascony, a region in France famous for being the home of foie gras, and is traditionally made by curing meat and slowly poaching in its own rendered fat. By vacuum sealing duck legs with just a few tablespoons of rendered duck fat, sous vide bypasses the need for the exorbitant amounts of fat used in this classic method. The result is crisp, tender meat with an intense duck flavor that requires no substantial cooking effort apart from waiting a very long time.
The recipe for the butternut squash purée is adapted from ChefSteps, which calls for cooking the sliced butternut squash sous vide in boiling water and blending the softened chunks with a small amount of xanthum gum. The idea behind this technique is that the purée is stabilized without needing to add butter or cream, allowing the pure, unadulterated flavor of butternut squash to come through.
Xanthum gum is a natural product carbohydrate that is criminally underrated as a thickening agent. It is flavorless, has potent thickening power, and is extremely stable over a wide range of temperatures and pH values. Whereas flour needs to be cooked to a roux and cornstarch needs to be made into a slurry and responds poorly to temperature changes, xanthum gum can simply be added to a sauce in a 0.1 to 1% weight ratio, depending on the viscosity desired. It is likely only a matter of time before it becomes a household name for thickening soups and sauces.
I don’t normally eat off of my pastry board, but I figured I would have had to clean it either way..
sous vide duck leg confit + butternut squash purée
- 2 duck legs
- 2-4 tbsp of rendered duck fat*
- 20g salt
Butternut squash purée:
- 1 medium butternut squash, peeled and sliced
- ½ tsp xanthum gum
- 1 tsp salt
Prior to cooking, vacuum seal the duck legs with 20g of salt and set aside in the refrigerator for 6 hours to cure.
Remove the duck legs from the bag, rinse with cold water, and pat the legs dry with paper towels. Transfer to a new bag and vacuum seal the legs with 2 – 4 tbsp of rendered duck fat. Immerse in a 160F water bath for 12 hours.
Remove the duck legs from the bag, and sear the duck on all sides in a hot cast iron or stainless steel skillet, seasoning with black pepper to taste. Keep in mind that the duck has already been cured, so additional salting is not necessary.
To make the butternut squash purée, vacuum seal the peeled and sliced squash and cook in boiling water for 20 – 25 minutes or until tender. If a vacuum sealer is not available, boil the squash directly in water for 15 – 20 minutes, or until tender.
Remove the squash from the bag, or if boiling directly, drain them in a colander, and transfer to a blender. Purée the squash with xanthum gum and salt until smooth. The purée can be served immediately or kept in the refrigerator for up to one week.
*Duck fat can be purchased online if not preparing legs from a whole duck. Otherwise, purified duck fat is easily obtained by cutting the unused skin scraps into rough 1″ squares and cooking them in a pot with 3-4 tbsp of simmering water. Cook the scraps for a total of 1 hour, after which the water will be evaporated, the fat rendered, and the skin turned into delicious, crispy cracklings. The full recipe can be found here.