1. Pop a pan of water on to boil and cook noodles in boiling water for 5-6 minutes, or until tender.
2. Heat an oiled wok over a high heat. Add beef in 150g batches. Stir-fry for about 1 minute, or until browned. Remove.
3. Heat same oiled wok over a high heat. Add carrot and bok choy stems. Stir-fry until stems are tender. Add onions and choy sum leaves. Stir-fry until wilted. Remove.
4. In a small food processor, or using a pestle and mortar, combine peanuts, juice from half the lime, soy sauce, chilli, sugar and a dash of water.
5. Cool wok slightly. Add peanut sauce and stir until combined and hot. Return beef and vegetables. Stir-fry until hot.
6. Serve noodles topped with beef and serve with lime wedges.