(Note: If your turkey is fresh, proceed to Step 2.) Defrost turkey: Place frozen turkey, still wrapped in plastic, into a cooler or stock pot large enough to hold it. Fill with enough cool water to completely cover the turkey. Keep turkey submerged in water for 30 minutes per pound, changing the water every hour.
When turkey is defrosted, unwrap, then remove neck and giblets; save them for gravy or stock, or discard. Choose a roasting pan large enough to hold the turkey with 2 inches of space between turkey and pan, all the way around. Place turkey on the rack in the pan and pat completely dry with paper towels, including inside the cavity. Let stand for 1 hour at room temperature before roasting. This ensures even cooking. Position oven rack in the lower third of the oven and preheat to 325 degrees F, preferably convection.
Stuff turkey, optional: Place your hand at the center of a sheet of cheesecloth, then push it into the cavity of the turkey to create a cheesecloth "bag." This will make the stuffing easier to remove after the turkey is cooked. Fill cavity halfway with your favorite uncooked stuffing (suggested recipe: "Crunchy Bread Dressing with Bacon & Leeks" in Williams Sonoma's Thanksgiving Sides School class). Tie cheesecloth closed with twine; trim and discard excess cheesecloth.
Prepare turkey for roasting: With the turkey lying breast side up, twist and tuck the wing tips underneath the turkey. Cross the legs, then tie together with kitchen twine. Generously spread softened butter all over to coat the entire bird. Season liberally with salt and pepper. Begin roasting the turkey, basting every 30 minutes (see Step 5 for instructions). The total roasting time will be 15 minutes per pound, unstuffed. If stuffed, add another 30 minutes cooking time for a bird under 16 pounds, and 30-60 minutes longer if it’s over 16 pounds.
How to baste: Remove turkey from the oven, opening and closing the door as quickly as possible to maintain the temperature. Baste turkey with juices that have accumulated in the pan, then place back into the oven. (Tip: For easier basting, tilt the pan to allow juices to collect on one side.) Begin taking the turkey's temperature about 1 hour before you expect it to be finished roasting. Turkey is done when a digital thermometer registers 165 degrees F at the thickest part of the breast (without touching the bone) and 175 degrees F at the thigh. Continue roasting, basting every 30 minutes, until the skin is golden brown. If the breasts begin to cook too quickly, cover them loosely with aluminum foil.
Finish roasting: If turkey is stuffed, cut the twine from the legs, pull the cheesecloth bag from the cavity, and transfer it to a bowl. Check the temperature of the stuffing: it should register 165 degrees F at the center. If it’s not done, remove cheesecloth and microwave the stuffing for 60 seconds at a time until it reaches 165 degrees F.
Rest turkey: Transfer the turkey to a carving board, cover loosely with foil, and let rest for 30 minutes before carving. (See the "How to Carve a Turkey" lesson for carving instructions.)