6 quarts heavily seasoned chicken or duck stock (there should be slightly too much salt and pepper to be used as a soup)
3 medium carrots, cut in cubes
3 onions, thickly sliced
1 head of garlic, paper-thin skin removed
1 cup rendered duck fat (see Note)
1 turkey, 10 to 12 pounds
1. Combine stock, carrots, onions, and garlic in a stockpot large enough to hold the turkey. Make sure it is filled no more than halfway. Bring to a boil over medium high heat.
2. While stock heats, rinse turkey and, starting at the neck, carefully separate the skin from the breast and upper thighs with your finggers, taking care not to tear the skin. Rub duck fat all over between skin and flesh, and then distribute truffle slices. Truss turkey. (Trussing is not mandatory but makes it easier to handle the bird later.)
3. When stock is boiling, add turkey, turn heat down so stock simmers, and cover pot with a lid if the entire turkey is not submerged. Simmer 40 minutes, then remove pot from heat, and let it slowly cool to room temperature, up to 4 hours. Store in a cool spot (about 40 degrees F) outside during the night (a garage, deck, or balcony), or refrigerate.
4. The next day, before your guests arrive, carefully take bird out of pot, place it on a rack in a roasting pan, and preheat oven to 475 degrees F. Put turkey in the oven, then 30 minutes later turn oven off, leaving the bird inside.
5. When you are ready to eat the main course, the bird will be perfectly cooked and nicely rested. The leftover stock can be strained and used as a a wonderful base for soups. (The turkey and vegetables will have reduced the saltiness of the stock, but taste before seasoning further.)
Use duck fat that you have rendered and saved in the freezer (it keeps up to 6 months), or order from D'Artagnan or from a local purveyor of fine meats and poultry.