Trim all fat and sheating from shanks. Rinse well and pat dry. Add all the ingredients except madeira, potatoes, and onions to a heavy casserole, or a dutch oven. Bring to a boil, reduce heat to low and simmer for 1 hour. Turn meat; add madeira and spoon juices over meat. Continue to simmer for 1 hour, basting meat periodically. Add the boiling onions and new potatoes; continue to cook until done. Done is when a fork pierces the potatoes easily; approximately 30 minutes. Serve with baby peas and a mint jelly.