1. Heat oven to 375 degrees F and place rack in lower third. In a small saucepan, over medium-high heat, stir together 1/2 cup broth, vinegar, sugar, Worcestershire and Tabasco until sugar is dissolved. Remove glaze from heat and add 2 Tablespoons butter; set aside.
2. Remove giblets from turkey and reserve neck bone. Pat turkey dry with paper towels. Place in a roasting pan with a rack and tuck back wings. Sprinkle body cavity with 1/2 tsp salt, 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 cup broth. Rub turkey with remaining 1 Tablespoon butter and 1 teaspoon salt. Tie legs together.
3. Cover pan with heavy-duty foil and seal around edges. Roast 1 hr. Reduce oven to 325 degrees F and roast 1 hr more. Remove foil and cut string between turkey legs. Roast, brushing with brown sugar mixture every 20 minutes, until an instant-read thermometer inserted 2 inches into inner thigh (without touching bone ) registers 170 degrees F, 1 1/2 to 2 hours more. (Cover any dark spots with foil as the turkey roasts to prevent burning and reheat glaze if butter begins to harden.). 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 mixture comes to a boil. Reduce heat and simmer 2 minutes more. Transfer to a bowl and serve with turkey.