Place beef strips 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. Cook beef, in batches, for 1- 2 minutes or until browned. Set aside on a plate.
Add remaining oil to wok over medium-high heat. Add ginger and onion and stir-fry for 1 minute. Add carrots and snow peas and stir fry for 2-3 minutes. Add bok choy, stir in oyster sauce and 2 tablespoons water and cook for 1 minute. Return beef to wok, add bean sprouts and half the dressing. Season and toss well to heat through.
Meanwhile, prepare noodles according to packet instructions. Drain.
Serve stir-fry with noodles, remaining dressing, chilli and coriander.
Vietnamese dressings are readily available at supermarkets and Asian grocers. Alternatively use a Thai-style dressing, sweet chilli sauce or your own spicy dressing.
When stir-frying beef wait at least 30 seconds before tossing - gives beef a chance to brown, giving it good colour and flavour. Second side will take a little less time to cook. When returning beef to the wok, careful it doesn’t boil in the liquid or it will toughen. Stir-fry only to combine and warm through.
Buy beef strips ready to go from the supermarket or butcher or slice your own at home.