Place beef in a large bowl or snap-lock bag, add half the oil and toss to coat. Heat a large wok or non-stick frying pan over high heat. Stir-fry beef, in batches, for 1-2 minutes or until browned. Set aside on a plate.
Add remaining oil to wok or pan over medium-high heat. Add onion and stir-fry for 1 minute. Add corn and brussels sprouts and stir-fry for 2-3 minutes. Add water chestnuts and bok choy and stir-fry for 1 minute. Stir in char siu sauce. Add 2 tablespoons water and cook for 1 minute. Return beef to wok, toss to heat through and season.
Prepare noodles according to packet instructions.
Serve stir-fry on top of noodles with sliced chilli, if desired.
Tips
When stir-frying the meat wait at least 30 seconds before tossing or stir-frying. This gives the meat a chance to brown, giving it good colour and flavour.
The second side will take a little less time to cook.
Once you return the meat to the wok, take care that it does not boil in the liquid or it will toughen. Stir-fry only to combine and warm through.
