Dissolve cornstarch in water; set aside. Fry Pork in covered, greased skillet until lightly browned. Drain all except 1 tablespoon oil. Add tofu, Mushrooms and Onion chunks. Combine soy sauce, Mushroom juice, Sugar and monosodium glutamate. Pour over ingredients in skillet. Bring to a boil. Continue cooking until sauce is blended into tofu, about 5 minutes. Stir in green onions and pour in cornstarch mixture. Cook until sauce is thickened. Serve with steamed rice.