1 med. size onion
4 tbsp. butter
1 lb. fresh mushrooms
2 tomatoes, fresh or canned
1/2 tsp. celery salt
1 c. sour cream
1/2 c. Parmesan cheese
1 tsp. salt
Cornflake crumbs (or cracker/bread crumbs)

Peel and thinly slice onion. Melt 3 tablespoons butter in large skillet and cook until soft, about 10 minutes. Slice mushrooms; put in pan and cook 10 minutes more, stirring occasionally. Cut up tomatoes (remove seedy pulp), add to mushrooms. Season with salts. Stir in sour cream and cook until thoroughly heated.

Place in oven proof serving dish, sprinkle with crumbs and cheese. Dot with remaining tablespoon butter. Bake at 350 degrees until top is browned (20-30 minutes).