1. Heat oven to 375 degrees F and place rack in lower third. In a small saucepan, heat 1 cup broth and 2 tbsp. butter until butter is melted; set aside.
2. Remove giblets from turkey and reserve neck bone. Rinse turkey inside and out; pat dry. Place in a roasting pan with a rack and tuck back wings. Sprinkle body cavity with 1/2 tsp. salt and 1/2 tsp. pepper; fill with onion, carrot, orange and herb sprigs. Fill neck cavity with onion and orange, if desired; secure skin flap under turkey. Place any remaining vegetables in bottom of pan with neck bone and 1/4 cup broth. Rub turkey with remaining 1 tbsp. butter, 1-1/2 tsp salt and 1/2 tsp pepper. Tie legs together.
3. Cover pan with heavy-duty foil and seal around edges. Roast 1 hour. Reduce oven to 325 degrees F and roast 1 hour more. Remove foil and roast, basting with broth-butter mixture every 30 to 45 minutes, until an instant-read thermometer inserted 2 inches into inner thigh (without touching bone) registers 170 degrees F, 2 to 2-1/2 hours. Remove turkey from oven, tent with foil and let stand 15 to 45 minutes before carving. Transfer turkey to a serving platter and remove rack from pan.
4. For gravy, remove vegetables and neck bone from pan, then strain drippings into a fat separator; pour off fat. Place roasting pan over 2 burners, add wine and heat over medium-high heat to deglaze, scraping up any brown bits in pan. Stir in pan drippings and transfer to a medium saucepan. Add 2 cups broth and bring to a boil. Stir together remaining 1 cup broth and the cornstarch; whisk into saucepan. Simmer, whisking constantly, until thickened, about 2 minutes. Transfer to a bowl and serve with turkey. Makes 18 servings.