Rub the turkey with generous amounts of salt and pepper—inside and out—and place it on a platter; cover and refrigerate for at least 4 hours. Remove the turkey from the refrigerator 45 minutes before roasting.
Preheat the oven to 475° with a rack in the lowest position. In a small bowl, mix together the softened butter and the chopped rosemary, thyme, and sage. Set the turkey on a rack in the bottom of a large roasting pan. Loosen the skin of the turkey by carefully slipping your fingers under the skin until you reach the end of each breast. Rub the herb butter under the skin. Stuff the cavity of the bird with the onion, celery, apple, and the remaining sprigs of rosemary, thyme, and sage.
Pour the chicken stock into the bottom of the pan, and transfer the turkey to the oven. Roast for 30 minutes, then reduce the heat to 250° and continue roasting the turkey for 3 to 5 hours (15 to 20 minutes per pound), or until an instant-read thermometer registers 165° when inserted into a thigh.
Transfer the turkey to a serving platter and let it rest for at least 30 minutes before carving.
While the turkey rests, make the gravy. Pour the drippings from the roasting pan into a large glass measuring cup or gravy separator, and set it aside to separate. Do not wash the roasting pan.
In a large saucepan, bring the chicken stock, water, and the reserved turkey neck and giblets to a boil over medium-high heat. Reduce the heat to low, and let the mixture simmer, uncovered, for 30 minutes. Strain the broth through a fine-mesh sieve, and discard the neck and giblets (or chop the giblets and set them aside). You should have at least 4 cups of stock.
Skim ¼ cup of fat from the top of the separated pan juices and place it in a large, heavy skillet. Set the skillet aside. Skim and discard the rest of the fat and return the de-fatted pan juices to the roasting pan over medium-high heat. Pour the wine into the roasting pan, scraping up any brown bits from the bottom, and boil the mixture until it has reduced to about ½ cup. Add 4 cups of the giblet stock and bring the mixture to a simmer. When the broth-wine mixture begins to bubble, pour it through a fi ne-mesh sieve into a large saucepan, discarding any solids. Place the saucepan over medium-low heat.
Place the skillet with the reserved fat over medium-high heat. Sauté the onion in the fat for about 15 minutes, stirring frequently, until it is translucent and beginning to brown. Stir in the fl our, reduce the heat to medium-low, and cook the roux, whisking constantly, for 3 minutes. Add the hot broth mixture to the roux in a fast stream, whisking constantly to prevent lumps from forming. Bring the mixture to a simmer and cook, whisking occasionally, for 10 minutes, or until the gravy has reached your desired consistency. If the gravy is too thin, whisk in additional giblet stock as necessary. If desired, stir in the reserved chopped giblets. Season the gravy with salt and pepper and transfer it to a heated gravy boat to serve.
Makes 10-12 servings