Heat 1 tbsp oil in a non-stick pan or wok and cook the cashews until golden. Scoop out of the pan then add the prawns and stir-fry until pink, about 2-3 minutes.
Scoop the prawns out then add the garlic, ginger, chilli, szechuan pepper and spring onions and stir fry for a couple of minutes.
Gradually mix the sauce ingredients into the cornflour and add 100ml water. Put the prawns and cashews back into the pan. Stir everything together then add in the sauce and toss until thickened. Serve with noodles or rice.