1.Combine sherry, sauce and sugar in medium bowl; add beef, toss to coat in marinade. Stand 10 minutes; drain. Toss beef in cornflour; shake off excess.
2.Meanwhile, cook rice in large saucepan of boiling water, uncovered, until just tender; drain. Cover to keep warm.
3.Heat vegetable oil in wok; deep-fry beef, in batches, until crisp. Drain on absorbent paper. Reserve oil for another use.
4.Heat sesame oil in same cleaned wok; stir-fry garlic, chilli and onion until onion softens. Add carrot and capsicum; stir-fry until just tender. Add gai larn; stir-fry until just wilted.
5.Add beef to wok with peppercorns, oyster sauce, extra soy sauce, stock and extra sugar; stir-fry until heated through. Serve beef and vegetables with rice.
It is easier to slice beef thinly if it is partially frozen.