For the tangerine gastrique: Combine the tangerine juice and vinegar in a medium nonreactive saucepan over high heat. Cook until reduced by half. Add the honey and continue cooking until reduced to 2 cups. Stir in the tangerine zest and salt and pepper to taste, and transfer to a bowl to cool. Reserve 1/4 cup for the gravy and use the rest for the turkey.
For the turkey a la tangerine: Remove the turkey from the refrigerator 1 hour before roasting. Preheat the oven to 450 degrees F.
Brush the entire turkey with oil and sprinkle liberally with salt and pepper. Sprinkle the cavity of the turkey with salt and pepper and fill with the parsley, rosemary, sage, thyme and half of the carrots, celery and onions.
Put 3 cups of the chicken stock in a medium saucepan and keep warm over low heat.
Place the remaining carrots, celery and onions on the bottom of a large roasting pan. Set the turkey on top of the vegetables and roast until lightly golden brown, about 45 minutes.
Reduce the heat to 350 degrees F and continue roasting, basting with the warm chicken stock every 15 minutes. When the breasts register 150 degrees F on an instant-read thermometer, begin basting the turkey with some of the gastrique. Continue roasting and basting with the gastrique until the breasts register 160 degrees F, 2 1/4 to 2 1/2 hours.
Remove the turkey from the oven and transfer to a baking sheet, keeping the oven at 350 degrees F. Remove the legs and transfer to a roasting pan. Tent the turkey loosely with foil and let rest 30 minutes before slicing.
Strain the pan drippings into a bowl and discard the solids. Add enough stock to make 4 cups liquid. In a pot over medium-high heat, bring the liquid to a simmer. Transfer the simmering liquid to the roasting pan with the legs, cover with foil and braise in the oven until tender, about 1 hour.
Remove the legs from the braising liquid and transfer to a baking sheet, reserving the braising liquid for the gravy. Switch the oven to broil. Brush the legs with some of the gastrique and place under the broiler until glazed and crispy, about 8 minutes.
For the gravy: In a saucepan, combine the turkey leg braising liquid with enough warm stock to make 7 cups and keep warm over low heat.
In a large saucepan over medium heat, heat the butter and oil until the oil begins to shimmer. Add the carrots, celery and onions and cook until soft, about 5 minutes. Add the garlic and cook for 30 seconds.
Whisk in the flour and cook until lightly golden brown, about 5 minutes. Whisk in the wine and cook until reduced by two-thirds. Whisk in the hot stock and black peppercorns and cook until thickened. Bring to a simmer and continue cooking, stirring occasionally, until the flour taste has been cooked out and the gravy coats the back of a wooden spoon, about 8 minutes.
Strain the mixture through a fine sieve into a clean saucepan, bring to a simmer and cook until slightly reduced. Add the reserved 1/4 cup tangerine gastrique, the orange liqueur and pink peppercorns and cook for an additional minute. Season with salt and pepper and stir in the tangerine zest. Serve the gravy alongside the turkey.