Updated Green Bean Casserole
4 tablespoons unsalted butter, divided
2 tablespoons flour
1 tablespoon sugar
1/4 teaspoon pepper
1/2 teaspoon salt                    
1 tablespoon onion, chopped
1 cup sour cream
2 cans whole green beans, drained
½ pound Swiss cheese, shredded
1 cup bread crumbs

Preheat oven to 350°F. Melt 2 tablespoons of butter. Add flour, sugar, pepper, salt and onion.

Stir in sour cream and heat through, but do not boil.

Stir in green beans and cheese, and pour into greased casserole.

Melt the remaining butter and stir in bread crumbs.

Top the casserole with the bread crumbs.

Bake for 20 minutes.