Add the turkey broth, onion, carrots, celery, turkey, salt, and pepper to the crockpot. Web slow cooker turkey soup with tarragon. Us 1 turkey carcass, broken into several pieces 2 quarts water 1 teaspoon salt 1⁄4 teaspoon pepper 1 onion, chopped 2 celery ribs, chopped 1 carrot,.