The recipe yield is:
Mix mashed potatoes with the cheeses with a mixer. Saute the onions in the margarine until soft. Add 1/3 of the onions to the potato mixture. Add salt to taste. Generously grease a 13"x9"x2" baking dish. Place a layer of lasagne noodles in dish, then a layer of potato mixture. Repeat layers, ending with noodles. Pour remaining cooked onions over all. Cover with foil and bake at 350 degrees until heated through.