2 tablespoons Dijon mustard
2 teaspoons chopped fresh rosemary
3 1/2 cups Turkey Stock, as needed
2. The next day, position rack in the lowest position of the oven and preheat to 325° F. Remove the turkey from the bag and rinse thoroughly under cold water. Pat the turkey skin dry.
3. Flavor Stuffing - Mix onion, celery, onion, rosemary, sage, and thyme in small bowl. Turn the turkey on its breast. Loosely fill the neck cavity with onion mixture. Using thin wooden or metal skewer, pin the turkey's neck skin to back. Fold the turkey wing tips akimbo behind shoulders or tie to body with kitchen string. Loosely fill the body cavity with onion mixture. Place the drumsticks in "hock lock" or tie together with kitchen string.
4. Place turkey, breast side up, on rack in the roasting pan. Rub all over with softened butter. Pour turkey stock into pan. Add the reserved turkey fat to pan.
5. Roast turkey, basting all over every 45 minutes or so with the pan juices, until a meat thermometer inserted in the meaty part of the thigh (but not touching a bone) reads 180° F, about 3 1/2 hours. Whenever the turkey stock has evaporated into a glaze, add 1 cup more stock or water to keep the drippings from burning. Tilt turkey so juices in body cavity run into pan. Transfer turkey to large serving platter and let stand for about 20 minutes before carving.
Gravy - Pour the pan drippings into a 1-quart gravy separator. Let stand 5 minutes. Pour drippings from separator into a 2-quart glass measuring cup. Add enough stock to measure 5 1/2 cups total. Measure 9 tablespoons fat from separator.
Place roasting pan over low heat and add 1 tablespoon turkey fat. Add shallots and cook until softened, about 1 minute. Add remaining 1/2 cup fat. Whisk in flour, scraping up browned bits in pan. Cook until lightly browned, about 2 minutes. Whisk in wine, then stock mixture. Bring to a boil. Reduce heat to medium-low and simmer, whisking often, until the gravy has thickened, about 5 minutes. Whisk in mustard and rosemary. Season with salt and pepper. Strain back into the 2-quart measuring cup. Pour into warmed gravy boat. Carve turkey and serve gravy alongside.