The lamb is first marinaded with soy sauce and rice wine mixed with cornflour. The cornflour is a bit of a 'secret weapon' in Chinese cooking. It actually breaks down the fibres in the meat so it tenderises it. This is perfect for fast cooking methods such as stir-frying. The official term for this is 'velveting'.
The lamb is fried and then left to rest while the cumin and chilli are toasted. Then the onion, ginger and garlic are quickly fried. Onion isn't authentic in this recipe, but I like to add it in for extra flavour and interest. Finally, the lamb is returned to the pan with the spices for a final heat through before serving.