Add a good drizzle of oil to a large (preferably non-stick) pot over medium-high heat. Add the meatballs and fry them until they get a nice crust on them, turning regularly. You don't need to cook them right through at this point, just ensure they caramelize/brown. Remove from pan and drain excess fat if needed (around 1 tbsp left is fine and will add flavour). Work in two batches if you need to.
Turn the heat down to medium and add the onion to the leftover fat. Fry until soft and golden, then add in sun dried tomatoes and garlic. Continue frying for another minute, then add in the tomato puree and fry for a minute or so.
Pour in the passata and swill out the jar with a little water, then pour in beef stock and Worcestershire sauce. Add the parsley, oregano, chilli flakes, salt, pepper and a good pinch of sugar (I do 1/2 tsp). Give it a stir and deglaze the pot with your wooden spoon. Stir in the meatballs (and all the resting juices) then turn the heat to low, pop on the lid and very gently simmer for 30mins, stirring once halfway. This will allow the meatballs to become soft and juicy and will also allow them release flavour into the sauce. If you're pushed for time even 10-15mins will help, just ensure you keep a heavy lid on so the sauce doesn't reduce.
Take off the lid, pour in the rice and give it all a good stir. Pop the lid back on and simmer for 15-20mins, or until the rice is cooked through, stirring occasionally. If you over reduce just add in a splash of water to help the rice cook through if needed.
Check for seasoning then serve up with any leftover parsley and a good helping of parmesan!