Swiss Style Green Beans

3 tbs butter
2 tbs flour
1 tsp salt
1/4 tsp pepper
1 tsp sugar
1 medium chopped onion
1 c sour cream
4 c fresh whole green beans cooked (can use canned)
1/2 lb swiss cheese
2 c cornflakes
1 tbs melted butter

Melt 3 tbs butter. Stir in flour, salt, pepper, sugar, and onion. Add sour cream gradually. Cook until thickened. Fold in green beans; heat thoroughly. Pour into greased casserole a layer of bean mixture, then a layer of grated Swiss cheese and another layer of green bean. Finish with grated cheese on top. Mix cornflakes in 1 tbs melted butter and sprinkle on top. Bake at 400° for 20 minutes.