In large mixing bowl combine, onion, bay leaves, celery salt, cayenne, salt, spinach, parsley, Worcestershire and butter. Blend well. Add cracker crumbs and sherry. Set aside. Put oysters in shells, if available. Top with above mixture. Sprinkle with grated cheese and bread crumbs. Top with small square of bacon. Put on cookie sheets and bake in preheated 400° oven until bacon is cooked, 15 to 20 minutes.