Preheat oven to 180°C. Heat a large non-stick frying pan with oil. Add lamb shanks and cook turning for 3-4 minutes. Add onions and cook for a further 2-3 minutes or until browned.
Place lamb shanks, onions and mushrooms in a large casserole dish.
Combine remaining ingredients and pour over lamb shanks. Cover casserole.
Cook in preheated oven for 1½ – 2 hours, stirring occasionally.
Serve with mashed potatoes and steamed green beans.