1 (15 pounds) turkey, heart, gizzard and liver chopped and reserved
2 cups apple cider
1 ½ cups kosher salt
2 cups dark brown sugar
3 sprigs rosemary
1 bunch(es) thyme
1 bunch(es) sage
3 pounds ice cubes
1 medium onion, finely chopped
2 celery ribs, finely chopped
1 large carrot, thinly sliced
10 cloves garlic
1 stick (plus 2 tablespoons) unsalted butter, softened
1 cup bourbon
2 tbsp canola oil
12 ounces (1 bag) pearl onions, thawed if frozen
3 cups turkey stock or low-sodium chicken broth
2 tbsp all-purpose flour
Put turkey in a brining bag set in a tub or very large pot. In a large saucepan, combine cider with salt, 1 cup of brown sugar, rosemary, thyme, and sage, and bring to a simmer, stirring to dissolve salt and sugar. Add 6 quarts of cold water to brine and pour over turkey. Add ice to brine and refrigerate turkey overnight. Preheat oven to 450ºF and set a rack on lowest shelf of oven. Drain turkey and pat dry. Discard brine. Fill turkey cavity with half of onion, celery, carrot, and garlic cloves; scatter remaining vegetables in a large roasting pan. Set a V-shaped rack in pan. Tie turkey legs with butcher’s twine and transfer bird to rack, breast side up. Add 2 cups of water to pan and roast turkey for 30 minutes.
Meanwhile, in a small saucepan, combine remaining 1 cup of brown sugar with 1 stick of butter and bourbon and heat just until sugar and butter melt. Reduce oven temperature to 350ºF and brush turkey with some glaze. Continue roasting turkey, brushing it every 15 minutes, for about 3 hours, until an instant-read thermometer inserted into thigh registers 165ºF; add another 2 cups of water and tent turkey with foil halfway through roasting. Transfer turkey to a carving board and let rest for 30 minutes. Strain pan juices into a heatproof bowl and skim off fat. (You should have about 1 cup.) Discard vegetables.
In a large saucepan, heat oil. Add chopped turkey giblets and cook over moderate heat until lightly browned, about 5 minutes. Add pearl onions and cook until lightly browned in spots, about 5 minutes longer. Add turkey stock and reserved turkey pan juices and bring to a boil, scraping up any browned bits from bottom of saucepan. In a small bowl, mash remaining 2 tablespoons of butter with flour and whisk it into gravy. Bring to a boil and simmer until gravy thickens, about 5 minutes. Whisk in roasted garlic. Carve turkey and serve with the gravy. Serves: 12.