Grease 9 x 13 inch pan. In a 1 quart saucepan, melt 2 tablespoons butter, stir in flour, salt, nutmeg and milk (and sherry). Cook over medium heat, stirring constantly until thick and bubbly, about 4 minutes. Stir in cheese until melted, set aside.

Season fish with celery salt and pepper. Toss bread crumbs with melted butter. Top fish with buttered bread crumbs and minced green pepper.

Broil fish until translucent, about 15 minutes, depending upon size of fish. Serve with sauce.