DRUM AU GRATIN WITH MUSHROOMS

2 lbs. freshwater drum fillets 2 T butter, melted salt and pepper to taste 1/2 lb. mushrooms, thinly slice 2 onions, sliced 1/2 C sour cream 5 T grated cheese 1 T bread crumbs Preheat oven to 400°F. Place fillets in a buttered 13x9x2” baking dish. Sprinkle with melted butter and salt. Bake  for 10 minutes. Saute the mushrooms with the onions until the onions are tender. Add salt and pepper to taste. Place over the fish. Pour sour cream over top and sprinkle with cheese and breadcrumbs. Bake 10 minutes or until fish flakes apart easily when tested with a fork. Serves 6.