Soak the oysters in warm water for 8 hours, and soak the mushrooms for 15 minutes in warm water and remove the stalks. Chop the oysters, bamboo shoots, water chestnuts and mushrooms into very small dice. Put all in a hot oiled frying pan and cook for 5 minutes, adding salt and pepper to taste. Fry for another 5 minutes, and add a little cornflour water. Chop the lettuce, put it in a basin and add the oyster mixture. Serve with Chinese sauce.