Add the remaining 2 tablespoons of oil and the garlic, sugar, onion and chopped ginger to the casserole and cook over low heat until the onion is deeply browned, about 7 minutes. Add the cilantro sprigs, star anise, Szechwan peppercorns and crushed red pepper and cook for 1 minute. Add the water, sherry and soy sauce and bring to a simmer. Return the veal shanks to the casserole and bring to a simmer. Cover and braise in the oven for about 3 hours, or until the veal is very tender.