Mix the cornflour and cayenne in a bowl, add the prawns and coat thoroughly, then mix in the soy sauce and leave in a cool place for about 30 minutes.
Spray some oil into a wok and place over a high heat, add the cashews and stir fry for 30 seconds or until golden, then remove them to a plate.
Next add the mushrooms and stir fry for 1-2 minutes until golden.
Add the prawns and stir fry for about 1-2 minutes, until they turn pink. Add the remaining Ingredients and stir fry for another minute.
Return the nuts to the pan, turn the heat down to medium, add the rice wine and a little water, then put a lid on the pan and cook for a further minute.