Place noodles in a heatproof bowl. Cover with boiling water. Stand 2-3 minutes, stirring to separate noodles. Drain.
Toss pork in a bowl with 1 tablespoon oil. Heat a large, non-stick wok or frying pan over a high heat. Add half the pork. Stir-fry about 2 minutes, until browned. Remove. Repeat with remaining pork.
Heat remaining oil in same wok. Add mushrooms. Stir-fry 3 minutes, until lightly browned and just tender. Add carrot, corn, shallots and ginger. Stir-fry 2 minutes.
Return pork to wok with noodles and choy sum. Toss over heat about 2 minutes until choy sum is just wilted.
Add combined sauces, chilli paste and 1 tablespoon water. Toss over heat until ingredients are coated in sauce and mixture is hot. Add cashews. Toss to combine.