Rub the cutlets with salt and plenty of pepper. Heat the butter in a heavy, covered casserole, add lamb and brown all over. Add the bay leaf, vinegar, orange juice and grated peel, bitters, hot pepper sauce, and a little stock if necessary to barely cover the lamb. Cover and cook over low heat until the lamb is tender, about 1½ hours.
Remove the cutlets to a serving dish and keep warm.