Mix the mince, onion, scallions, chilli oil (if using) and seasoning well together. With wet hands shape into small meatballs the size of a walnut. Fry the meatballs in a large pan with a little oil until nicely browned. Set aside while you make the Tomato and Ginger Sauce. If time does not permit, there are many varieties of sauces and salsas in store. Put the garlic, ginger, cider vinegar and brown sugar into the processor and whiz for a minute. Pour the mixture and the tin of tomatoes into a saucepan and bring to the boil. Reduce the heat, add the meatballs and simmer gently for 10 minutes. Season and add coriander just before serving. Serve with rice or potatoes and a green salad.