To make the marinade, mix the egg white, soy sauce and vegetable oil, add the beef, and leave for 30 minutes.
Heat a wok until just smoking. Add the vegetable oil and, when hot, stir-fry the beef until well browned. Remove from the wok and drain on paper towel. Add the onion, garlic and capsicum to the wok and stir-fry until fragrant. Deglaze the wok with the shaoxing a