To make brine for a turkey, combine 2 gallons cold water with 2 cups kosher salt and 2 cups sugar in a large pot. This recipe should make enough brine for a 12- to 18-pound turkey.
Once the sugar and salt are fully dissolved, place the turkey in a container, and then pour the brining liquid over it, making sure that the entire turkey is fully covered. Place the turkey in the brine in the refrigerator and let it sit for 18 to 24 hours.
Once the turkey has been brined, remove it from the refrigerator and discard the brining liquid. Pat the turkey dry with paper towels. If the turkey is going to be roasted within two hours, it can remain sitting out until it is ready to be cooked. However, if it is not going to be cooked for more than two hours, the turkey should then be put back into the refrigerator until it is time to cook it.
For a more flavor-filled brine, combine 1 quart of water with 1 1/2 cups coarse salt, 6 bay leaves, 2 tablespoons whole coriander seeds and 1 tablespoon dried juniper berries in a saucepan. Add 2 tablespoons whole peppercorns, 1 tablespoon fennel seeds and 1 teaspoon mustard seeds, and bring the mixture to a simmer. Stir the solution until the salt dissolves.
Meanwhile, line a 5-gallon container with a brining bag. Place an 18- to 20-pound turkey in the bag along with the cooled salt and herb mixture and 24 cups water. Stir in thinly sliced onions, fresh thyme and crushed garlic cloves. Tie the bag, and refrigerate the turkey for 24 hours.
Alternatively, prepare a dry brine for the turkey by adding 10 sprigs of thyme, 6 sprigs of sage and 4 sprigs of rosemary in a food processor. Add 4 cloves garlic, 2 teaspoons celery seeds and 1/2 teaspoon black pepper. Stir in 1/2 cup kosher salt and 2 tablespoons granulated sugar to the mixture. Rub the dry brine over the turkey's skin, and refrigerate it uncovered for six to seven hours.
Brining a turkey requires a container that is large enough to hold the turkey and the brine. However, if this is not available, it is also possible to brine it in a large plastic bag. Numerous brining kits are available that contain the necessary ingredients and a brining bag.