Remove giblets and neck from turkey; set aside. Rinse turkey thoroughly with cold water, and pat dry. Loosen skin from breast without detaching it; carefully spread butter mixture under skin. Rub outside of turkey evenly with 1 tablespoon salt and 1 tablespoon pepper.
Spoon 4 cups Sausage-and-Wild Mushroom Stuffing into turkey; truss turkey, and tie ends of legs together with string. Lift wingtips up and over back, and tuck under bird. Place turkey, breast side up, in a large roasting pan; rub with 2 tablespoons soy sauce and oil.
Bake at 375° for 2 1/2 hours or until meat thermometer inserted into turkey thigh registers 180° and stuffing registers 165°, shielding turkey with aluminum foil after 1 hour and basting with pan juices every 30 minutes.
Cook giblets and neck in boiling water to cover 45 minutes or until tender. Drain, reserving 1 cup broth. Coarsely chop neck meat and giblets; chill.
Transfer turkey to a serving platter, reserving drippings in pan. Remove and discard fat from drippings; pour 1/4 cup drippings into a heavy saucepan. Stir wine and reserved broth into roasting pan, stirring to loosen particles.
Place 1/4 cup drippings over medium heat. Add flour, and cook, whisking constantly, until browned. Gradually add wine mixture and half-and-half; cook mixture, whisking constantly, until bubbly. Stir in neck meat and giblets, 1/2 teaspoon soy sauce, salt, and pepper; simmer, stirring often, to desired thickness. Serve gravy with turkey. Garnish, if desired.