Potato Casserole

8 boiled and cubed potatoes 1/4 cup butter 1 can cream of celery soup 1 pint sour cream 1/2 cup chopped green onions 1 cup grated cheddar cheese Heat all ingredients except potatoes until cheese melts. Mix sauce with potatoes and put in 2 quart ungreased casserole. Top with dots of margarine and cover with thin layer of corn flakes. Bake uncovered at 350 degrees for 45 minutes. Serve and enjoy.