2 (5 1/2- to 6-pound) Pekin ducks, trimmed of excess fat, necks, gizzards, and hearts reserved Kosher salt Freshly ground black pepper 1 cup water 1 tablespoon vegetable oil 2 medium carrots, coarsely chopped 2 medium tomatoes, coarsely chopped 2 celery ribs, coarsely chopped 1 small leek, white and pale green parts only, coarsely chopped…