How to Make It
In a bowl, toss the carrots, onions, celery, apples, thyme and rosemary. Rub the turkey inside and out with the vinegar; season with salt and pepper. Add one-third of the vegetable mixture to a large pot. Top with the turkey legs and half of the remaining vegetable mixture. Set the turkey breast on top and scatter the remaining vegetables over the breast. Cover and refrigerate overnight.
In a medium bowl, combine all of the ingredients and mix well. Keep chilled but still spreadable.
Remove the turkey from the pot. Spread half of the vegetable mixture in a roasting pan and the other half on a rimmed baking sheet. Set the turkey breast on the vegetables in the roasting pan and the legs on the baking sheet. Let stand at room temperature for 1 hour.
Preheat the oven to 350°. Separate the turkey skin from the breast meat. Spread the herbed fat under the skin of the breasts, pressing to distribute it evenly. Tuck the wings under the breast. Roast the legs for 2 hours and the breast for 2 hours and 15 minutes, basting occasionally. The turkey is done when an instant-read thermometer inserted in the inner thigh registers 165° and the thickest part of the breast registers 160°. Let rest for 30 minutes. Carve and serve.
Ask your butcher to separate the whole legs from the bird, keeping them connected at the back bone. Rendered duck fat is available at specialty food stores and online at cybercucina.com.