Molasses-Brined Turkey with Gingersnap Gravy

5 cups low- salt chicken broth

2 medium carrot s, chopped

2 large celery stalks, chopped

1 onion , halved

2 small bay leaves

18- to 20-pound turkey Brine and turkey

1 18- to 20-pound turkey

7 quarts water

2 cups coarse salt (about 9 ounces)

1 cup (packed) dark brown sugar

1 cup mild-flavored (light) molasses

2 bunches fresh thyme

1 bunch fresh sage

2 quarts ice cubes

2 large onion s, halved

1 head of garlic , halved horizontally

3 tablespoons olive oil

1 tablespoon ground black pepper

1 tablespoon chopped fresh sage

4 cups (about) low- salt chicken broth Gravy

1 cup finely chopped onion

1 tablespoon chopped fresh thyme

20 gingersnap cookies, coarsely crumbled (about 1 3/4 cups)

3 to 4 tablespoons apple cider vinegar

1 teaspoon Worcestershire sauce

1/4 cup whipping cream