Remove turkey from refrigerator and let stand for 2 hours at room temperature.
Place rack on lowest level in oven. Heat oven to 450 degrees. In a medium bowl, combine melted butter and white wine. Fold a large piece of cheesecloth into quarters; cut it into a 17-inch, four-layer square. Immerse cheesecloth in the butter-and-wine mixture, and let soak.
Working on a large piece of parchment paper, fold wing tips under turkey. Sprinkle 1/2 teaspoon salt and pepper inside turkey. Fill large cavity and neck cavity loosely with as much stuffing as they hold comfortably -- do not pack tightly. (Cook remaining stuffing in a buttered baking dish for 45 minutes at 375 degrees.) Fold neck flap under, and secure with toothpicks. Tie legs together loosely with kitchen string (a bow is easy to undo later; it is not necessary to make a tight knot). Rub turkey all over with the softened butter.
In a heavy, metal roasting pan (sides should be 2 to 3 inches high), place parsnip, onion, celery, carrots, celeriac, and white turnip. Place roasting rack on top of vegetables, then place turkey, breast side up, on roasting rack. Sprinkle turkey with remaining 1 1/2 teaspoons salt and pepper.
Lift cheesecloth out of liquid, and gently squeeze it, leaving it very damp. Spread folded square of cheesecloth evenly over breast and about halfway down sides of turkey; it can cover some of leg area. Place turkey, legs first, in oven. Cook for 30 minutes. Using a pastry brush, baste cheesecloth and all exposed parts of turkey with butter-and-wine mixture. Reduce temperature to 350 degrees. Cook 2 1/2 more hours, basting with pastry brush every 30 minutes and watching the pan juices; if pan is getting too full, spoon out juices so level remains below the rack.
After this third hour of cooking, remove and discard cheesecloth. Turn roasting pan so the breast faces back of oven. Baste turkey with juices that have collected in bottom of pan. If there are not enough juices, continue to use the butter-and-wine mixture. The skin gets fragile as it browns, so baste carefully, particularly over the breast. Cook another hour, basting every 30 minutes. If some areas of the bird start getting too brown, cover those areas loosely with aluminum foil.
After fourth hour of cooking, insert an instant-read thermometer into thickest part of thigh. Do not poke into a bone. The thermometer should reach at least 180 degrees and the turkey should be golden brown. The breast does not need to be checked for temperature. If turkey is not golden brown or the thigh meat does not register 180 degrees, baste turkey, return to oven, and cook another 20 to 30 minutes. Insert the instant-read thermometer into the center of the stuffing. Temperature should read from 140 degrees to 160 degrees.
When fully cooked, transfer the turkey to a serving platter, and let rest for 20 to 30 minutes. Make gravy using the vegetables while the turkey rests.
Melt butter in a large skillet. Add onions and celery, and cook over medium heat until onions are translucent, about 10 minutes. Add sage, stir to combine, and cook 3 to 4 minutes. Add 1/2 cup stock, and stir well. Cook for about 5 minutes, until liquid has reduced by half.
Transfer onion mixture to a large mixing bowl. Add all remaining ingredients, including the remaining stock; mix to combine.
Yield: 12 cups