Combine all the meatball ingredients in a mixing bowl except the bocconcini and olive oil. Season. Mix everything together until well combined and sticky. Divide mixture into four portions, 200 grams each. Roll into meatballs. Then use your thumb to make a deep dent in the center of each meatball. Fill with a bocconcini, pinch mince together to seal cheese inside then roll back into a giant meatball.
Heat oven to 150ºC. Heat 2 tablespoons olive oil in a frying pan over medium heat. Add meatballs to the pan in batches, cook for 5 minutes or until browned on all sides. Then place meatballs on a tray lined with baking paper and transfer to the oven while you prepare the sauce.
Heat another tablespoon of olive oil over medium-high heat. Add onion and garlic, sauté for 3 minutes or until onion is soft and translucent. Then add tomato paste, keep stirring and cook for 1 minute.
Add crushed tomatoes, chilli flakes, bay leaves, thyme leaves and 1 cup water, season and stir well.
Turn the heat to medium, add the meatballs to the sauce, stir gently until all meatballs are nicely coated in the sauce. Cover the pan slightly with a lid and simmer for 15-20 minutes until the sauce thickens.
Meanwhile, cook spaghetti according to package instructions.
Drain pasta through a colander, and put the back in the same pot. Add a cup of the marinara sauce to the pasta and stir well.
To serve, dish the spaghetti and place each meatball on top. Ladle extra marinara sauce over the meatball and pasta, sprinkle with parsley and grated parmesan.
