If your meat is not already minced, whiz it up in a food processor to the required consistency and place it in a bowl.
Use the food processor to turn the bread into breadcrumbs, then add to the meat.
Bash up the cumin seeds and dried chilli in a pestle and mortar, and pick and finely chop the rosemary leaves. Add to the mince with the dried oregano and egg yolk. Season well with sea salt and black pepper.
At this stage you could add your optional ingredients (peeling and finely chopping the onion and garlic first, then cooked together gently in 1 tablespoon of oil until tender and allowed to cool).
Mix well, and, with wet hands, roll and pat into meatballs the size and shape you want (cook straight away or put on greaseproof paper and refrigerated for up to a day.)
Preheat the oven to 200°C/400°F/gas 6 and heat a thick-bottomed casserole pan on the hob.
Swirl 4 tablespoons of oil around the pan and add your meatballs. Fry until brown all over, being careful not to break them up.
Turn the heat down and cover with the Basic tomato sauce, pick the basil leaves and tear in fresh basil, tear over the mozzarella and finely grate over the Parmesan.
Cook in the oven for about 15 to 20 minutes, or until the cheese is golden.