Blanch the peas for about five minutes, and drain them. Blanch the lettuce for one minute. Put peas and lettuce in a saucepan with the butter, stir gently on the fire for about one minute, and then add a little broth or water, the parsley, salt, and pepper; boil slowly till done, and serve warm. The parsley may be served, or removed just before serving, according to taste. The lettuce is always served with the peas.