Lyonnaise Potatoes

Cook one onion, thinly sliced, in three tablespoons butter until delicately browned. Remove onion and keep in a warm place. Add three cups cold boiled potatoes cut in slices, sprinkle with salt, pepper, and stir until well mixed with butter. Press to one side of spider and let brown richly underneath, then sprinkle onions over potatoes, let heat thoroughly, then turn on a hot serving platter top side down; sprinkle with finely chopped parsley. Cooking the onion separately lessens the danger of burning the onion.