Wash and blanch the heels, and simmer gently in stock or water until the bones can be easily separated from the meat—about 3 hr. Remove the bones and press the meat between 2 plates until cold. Then cut into pieces about 1½ in. square. Dip the pieces into the seasoned flour. Beat the egg and add to it the finely-chopped parsley and lemon rind. Add a little milk if mixture is too dry. Coat the pieces of meat thickly with the egg mixture and toss in breadcrumbs. Fry in hot, deep fat until golden brown. Serve hot, garnished with parsley.