Heat oven to 375 degrees 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 Tbsp butter; set aside.
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 turkey cavity with 1/2 tsp salt; fill with onions, carrots, orange wedges and herb sprigs. Fill neck cavity with onion and orange; secure skin flap under turkey. Place remaining vegetables in pan with neck bone and 1/4 cup broth. Rub turkey with remaining 1Tbsp butter and 1 tsp salt. Tie legs together.
Cover pan with heavy-duty foil and seal around edges. Roast 1 hr. Reduce oven to 325 degrees and roast 1 hr. more. Remove foil and roast, brushing generously with brown sugar mixture every 20 minutes, until an instant-read thermometer inserted 2 inches into inner thigh (without touching bone) registers 170 degrees, 1-1/2 to 2 hr. more. (Cover any dark spots with foil as the turkey roasts to prevent burning.). Remove turkey from oven, tent with foil and let stand 15-45 minutes before carving. Transfer turkey to a serving platter and remove rack from pan.
For gravy, remove vegetables and neck bone from pan, then strain drippings into a fat separator; let sit 5 min, then pour off fat. Place roasting pan over 2 burners, add wine and heat over medium-high heat to deglaze, using a whisk to scrape up any brown bits in pan. Stir in 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 min. Transfer to a bowl and serve with turkey.
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