Shuck 4 to 6 oysters per guest and leave on the half shell. Finely chop toast, onions and top, parsley and crabmeat and add butter. Add Parmesan cheese and mix well. Place oysters on sheet pan and bake at 375 degrees until slightly curled. Remove from oven and make a thin patty of crabmeat mixture and cover oysters. Return to oven and let brown slightly or until hot through. Serve hot on rock salt or napkined plates. Yields 4 to 6 servings.