Spread the frozen potatoes in the bottom of a 13 X 9-inch casserole dish lightly sprayed with cooking spray.
In a medium size bowl mix together the soup, sour cream, and cheddar cheese.
Pour a ¼ cup of the melted butter over the potatoes and spread the soup mixture over the top.
In a medium size, bowl mixes the remaining butter into the cornflakes and spread the mixture over the casserole. Cover with aluminum foil and bake for 1 hour. Remove foil and continue baking until cornflakes start to brown and potatoes are done.