POTATOES LYONNAISE

Take 5 or 6 cold boiled potatoes and cut them in slices. Put 1 tablespoon of butter in a frying pan, and when it is melted add 2 thinly sliced, medium-sized onions, and fry these, letting them cook very slowly ten minutes; then season with pepper and salt and add the sliced potatoes, and let these fry slowly, turning with a knife until they are a golden brown; season afresh with pepper and salt, and add 1 tablespoon of finely chopped parsley before serving. These potatoes will take a great deal of salt and pepper.