Mix the salt, thyme, bay leaf and pepper in a small bowl.
Rub the mixture on the duck legs and let it sit, uncovered, in the fridge overnight.
Heat a sous vide water bath to 155F degrees.
Place the duck legs in a vacuum sealable bag (or freezer bag if using the water displacement method) and add the garlic, shallots, duck fat and champagne vinegar.
Vacuum seal the bag and place it in the water bath. Cook for 32-36 hours (the longer it cooks, the softer the meat will be).
About 30 minutes before the duck is done, place the mushrooms on a large baking sheet and toss them with the olive oil and salt.
Roast them in the oven on 450F degrees for 20 minutes, stirring once halfway through.
Remove the bag from the sous vide water bath and place it in an ice bath for 10 minutes.
Remove the duck from the bag (reserving juices) and place it in a cast iron skillet, skin side up.
Place the garlic and shallots in the pan and drizzle about ¼ cup of the liquid from the bag over the top.
Broil on high until the skin is golden brown, about 7 minutes. Be careful not to burn or overcook the legs.
Serve the duck over mashed potatoes, polenta or rice, drizzled with the pan sauce and topped with the roasted mushrooms.
Optional: drizzle a touch of hazelnut oil over the top.
Notes
Removing air from the sealable bag is essential for food safety. This will keep bacteria out of the bag, especially for longer cooks like this duck confit.
Since the duck legs cook for up to 36 hours, you’ll want to ensure the water level stays high so the duck remains submerged in water. Add more water if necessary or cover the water bath to reduce water evaporation.
The bag of duck legs may start to float. If this happens, you can open the bag to let the excess air out, then reseal it. (This works for a vacuum sealed bag or a ziploc bag).
You can also prevent floating by using a sous vide sinker weight or weighing the bag down with something heavy like a wet towel.
Make sure you broil the duck legs skin side up so the skin gets browned and crispy.
Be careful not to broil the duck legs for too long as they may burn or dry out.