Season the meatballs with salt and pepper
Finely chop the onion and garlic
In a large frying pan / wok / heavy based saucepan fry the meatballs in the oil until browned
Remove meatballs from pan into a bowl to rest for a bit
Fry the pancetta until it starts to go golden, then add the onion and garlic
When the onion is translucent add the meatballs back in and mix together
Mix in the passata and herbs
Simmer for at least an hour, adjust seasoning as required. Top up with a little boiling water if it starts to dry too much. (I use the slow cooker, as it simmers without needing stirring and doesn't loose moisture)
Serve with the cooked spaghetti, garnish as desired with the parsley