Potato Cassarole

6 medium potatoes boiled in skins. Peel and dice. Fill bottom of buttered cassarole dish with potatoes. Mix the following together in a bowl: ¼ c melted butter, 1 can cream of chicken soup, ½ c milk, ½ pint sour cream, 1/3 c chopped onion, ½ c grated cheese. Pour over potatoes. Mix together ½ c melted butter and 2 cups crushed corn flakes. Place on top. Bake uncovered 30-40 minutes at 350 degrees.