Combine soup, milk, onions, salt, and pepper. Blend well.
Place half of the sliced potatoes into a two quart casserole. Add half of the wurst, and cover with half of the soup mixture. Repeat layers and spat with butter or margarine. Cover casserole and bake at 350F for about 1 hour and 15 minutes. Remove cover and sprinkle with cheese. Bake uncovered for 10 minutes longer, or until potatoes are tender.
