Heat the oil in a non-stick frying pan. Sauté the spring onions, lemongrass, garlic and ginger for approx. 5 mins. Add the soy sauce and vinegar, mix, transfer to a bowl, leave to cool. Add the mince and breadcrumbs, knead thoroughly by hand until the ingredients form a compact mass, shape into approx. 25 balls.
Heat the oil in the same pan. Fry the meatballs in batches for approx. 6 mins. all over. Remove from the pan.
Mix the soy sauce with all the other ingredients up to and including the cornflour. Pour into the same pan, bring to the boil while stirring, simmer for approx. 2 mins. Return the meatballs to the pan, simmer for approx. 3 mins., turning frequently. Sprinkle with the reserved onion greens.