1) In a large bowl, mix together all the ingredients, except the rapeseed oil. Shape heaping tsp of the mixture into 2cm balls.
2) In a Dutch oven or casserole, heat a tbsp of oil over a medium-high heat. Working in batches, wiping the pan in between, saute the meatballs, turning frequently for even browning, until cooked through, about 4 to 5 minutes. Place on a paper towel-lined plate.
For the sauce:
1) Heat the oil in the same pan over a medium-high heat. Add the onions and saute until golden brown, about 8 minutes.
2) Add the chilli flakes and cook 1 minute. Stir in the remaining ingredients and reduce the heat to low.
3) Add the browned meatballs to the pan and toss gently to coat with sauce.