Slice liver thin and mix with corn starch and crushed garlic. Brown quickly in hot oil. Add finely-sliced onions and mushrooms. Stir-fry until meat is evenly browned, then add chopped scallions and soy sauce. Continue cooking with constant stirring for 6 to 9 minutes. A tablespoon of brandy may be added to the meat just before frying for that little touch of luxury the Chinese lavish on honored guests.