For the Chinese beef, cut the meat into strips (1 x 4 cm) and sprinkle with cornstarch. Stir through all marinade ingredients and pour over the meat.
Cover and marinate in the refrigerator for half an hour and drain through a sieve.
Stir through pineapple or orange juice and cornstarch in a saucepan. Add remaining ingredients and bring to a boil, stirring. Season the sauce and set aside with the lid on.
Heat oil in a wok or wide frying pan, fry the meat in batches for about 3 minutes, turning repeatedly, remove the meat and keep warm.
Cut onion, radish and carrots into fine strips, stir-fry with pineapple cubes in the same frying pan for 3-5 minutes. Mix the meat, sauce and vegetables and bring the Chinese beef to the table quickly, preferably with rice.