1.Place noodles in large heatproof bowl and cover with boiling water. Use fork to separate noodles, then drain. Rinse again by pouring boiling water over noodles in colander; drain.
2.Heat half of the peanut oil in a wok and stir-fry chilli and garlic briefly, until just fragrant. In batches, add prawns and stir-fry over high heat until just changed in colour.
3.Heat remaining peanut oil in wok. Stir-fry noodles and buk choy over high heat until buk choy just wilts.
4.Return prawns to wok with the water, sesame oil, kecap manis, sauce and coriander. Stir-fry briefly over high heat until prawn mixture is just hot.