Mix together all the ingredients for the meatballs and chop for a few seconds in a food processor.
Using floured hands, form into about 20 meatballs.
Heat the oil in a frying pan and sauté the meatballs, turning occasionally, until browned and sealed (10 to 12 minutes).
Sweet and Sour Sauce:
Mix together the soy sauce and cornflour in a small bowl.
Heat the oil in a pan and sauté the onion for 3 minutes. Add the red pepper and sauté, stirring occasionally, for 2 minutes. Add the tomatoes, vinegar and sugar, season with pepper and simmer for 10 minutes.
Add the soy sauce mixture and cook for 2 minutes, stirring occasionally.
Blend and sieve or puree the sauce through a mouli.
Pour the sauce over the meatballs, cover and simmer until cooked through (about 5 minutes).