Brown meat in vegetable oil. Add soy sauce, Msg, stock, and sugar. Allow meat to cook in sauce for about 2 minutes. Add onion and celery and let cook for a couple more minutes. Add mushrooms, bamboo shoots and green onions and cook from three to five minutes. Push food to side of pan and add shiratake. Cook until shiratake absorbs some of the juice Add watercress and cook for one minute. Stir well and serve with rice.