1. Grind the peppercorns.
2. Put the sesame oil in a wok and stir fry the white part of the spring onions, the ginger and garlic for 1 minute.
3. Add the prawns and the peppercorns and stir fry for another 1 minute, then add the sherry, soy sauce, chilli sauce, tomatoes and sugar.
4. Cover and cook for 3 minutes.
5. Sprinkle with the green part ofthe onions and serve.