Heat lard in heavy skillet (bacon drippings or other fat or oil may be used). Arrange in skillet a layer of potatoes, then one of onions; repeat.
Sprinkle with salt and pepper. Sauté, covered, over low heat, about 15 minutes. Uncover; increase heat slightly and sauté 10 minutes longer, or until potatoes are crisp and brown on underside. Do not stir.
Sprinkle with parsley. Fold in half like an omelet and serve on a hot platter.