Mix all the sauce ingredients in a bowl and set aside.
Heat a wok and add the oil until it starts to smoke. Add the chicken, onions, garlic, chillies and cashew nuts and stir fry over a high heat until everything starts to brown. Add the water, pouring it in round the sides of the wok, and then add the sauce ingredients. Allow to bubble and stir well to mix. Mix in the spring onions and serve with steamed rice.
This recipe is from the Chiang Mai cookery school in Thailand.