2 tablespoons butter or margarine2 tablespoons flour1 teaspoon salt1 teaspoon sugar1 teaspoon minced onion1 cup sour cream4 cups green beans, canned or frozen½ cup water chestnuts, sliced and drained8 ounces shredded Swiss cheese2 tablespoons melted butter or margarine1 cup corn flake crumbsMelt 2 tablespoons butter or margarine. Stir in flour, salt, sugar, and onion. Add sour cream and stir until all ingredients are blended and thickened.Gently mix in beans and water chestnuts. Place in a greased 1½ quart casserole dish. Sprinkle the cheese over the beans. Mix the cornflake crumbs with melted butter or margarine. Top the cheese with this mixture.Bake at 350 degrees for 20 to 30 minutes.Makes 4 to 6 servings.