In a 3 quart saucepan combine 2 tablespoons melted butter, flour, onion, sugar, salt, pepper, sour cream and 4 ounces of the cheese. Cook over low heat and stir constantly until thickened. Fold in green beans. Pour into a 2 quart casserole dish and sprinkle the rest of the cheese on top.
In a small bowl combine cereal crumbs and melted butter; sprinkle over beans.
