How to Make It
In a food processor, pulse 8 of the garlic cloves with the salt, thyme and lemon zest until finely chopped. Add the juniper berries and peppercorns and pulse just until slightly cracked.
Preheat the oven to 325°. Arrange the turkey legs in a large roasting pan and rub with the seasoned salt. Let stand for 30 minutes. Pour the duck fat and vegetable oil over the turkey legs and add the remaining 4 garlic cloves to the pan.
Roast the turkey legs for about 2 hours, turning them every 30 minutes, until the meat is very tender and pulls away from the drumsticks. Transfer the legs to a large pot and carefully strain the fat over them, stopping when you reach the sediment and any caramelized pan juices. Reserve the garlic cloves. Let the turkey legs cool to room temperature, then refrigerate overnight or for up to 5 days.
While the turkey legs are cooling, return the garlic to the roasting pan and set the pan over 2 burners. Add 2 cups of the stock and bring to a simmer over moderately high heat, scraping up the browned bits on the bottom and sides of the pan and mashing the garlic into the juices. Strain the pan juices into a large measuring cup, let cool then refrigerate for up to 5 days.
To serve the confited turkey legs on Thanksgiving Day, preheat the oven to 350°. Gently rewarm the turkey legs in the large pot over moderate heat, just until the fat melts. Remove the legs from the fat and transfer them to a roasting pan; reserve 2 tablespoons of the fat. Roast the turkey legs for 25 minutes, turning once or twice, or until golden and crisp in spots. Transfer the turkey legs to a platter, cover loosely with aluminum foil and keep warm.
Pour off any fat from the roasting pan and set the pan over 2 burners. Add the remaining 2 cups of stock and the reserved pan juices and bring to a boil, scraping up any browned bits stuck to the bottom and sides of the pan. Pour the pan juices into a medium saucepan and bring back to a boil.
In a small bowl, blend the flour with the reserved 2 tablespoons of fat. Whisk the flour paste into the pan juices and simmer over moderate heat, stirring, until the gravy thickens and no floury taste remains, about 10 minutes. Stir in the balsamic vinegar and season lightly with pepper. Serve the turkey legs with the garlic gravy.
Duck fat is available at some specialty markets or you can mail-order it from D'Artagnan (800-327-8246). The unique flavor imparted by this luxurious fat is worth the effort of finding it. Duck fat is also economical, as it can be strained and reused many times. Store it in the freezer for up to 1 year.