Melt butter in casserole pot or large frying pan over low heat. Stir in onion, carrot and celery; cook for 5 minutes or until soft and golden. Remove vegetables and set aside.
Pat the veal shanks with a kitchen paper to remove excess moisture; dust with flour and season with salt and pepper. Increase the heat; brown veal shanks on all sides. Remove and set aside.
Pour in wine; stir to remove any cooked bits of meat that are stuck to the sides of the pan. Add beef stock and cooked vegetables back into the pan. Cover and simmer for 30 minutes, adding more stock if necessary.
Mix tomato puree with 1 tablespoon hot water and stir into casserole. Return veal shanks to the casserole and braise in the oven for 3 hours or until the meat is fork tender.
About 10-15 minutes before serving, stir in grated lemon rind and parsley.