1 (10 3/4 oz.) can condensed cream of mushroom soup
2/3 c. milk
2 tbsp. onion, finely chopped
4 oz. (1 c.) Cheddar cheese, shredded
4 med. (4 c.) peeled potatoes, thinly sliced
1 tbsp. butter

Heat oven to 350 degrees. Lightly grease 1 1/2 quart casserole. In large bowl, combine soup, milk and onion; using wire whisk. Blend well. Stir in cheese and potatoes. Spoon into greased casserole. Dot with butter. Bake at 350 degrees for 1 to 1 1/2 hours or until potatoes are tender.