1. Combine all meatball ingredients in a large mixing bowl and gently mix together until ingredients are well combined. Shape into 3cm balls and place in the fridge for 30 minutes.
2. Heat the olive oil and butter together in a large, heavy bottomed saucepan over a medium heat. Cook the onion for 6-7 minutes until onion softened and almost transparent. Add the garlic and cook for one minute.
3. Add the stock, tinned tomatoes, sugar, basil, Italian seasoning, bay leaves, oregano and chilli flakes. Gently add the meatballs. Stir and bring to a boil, then reduce the heat to a simmer and cook for 30 minutes.
4. Add the pasta and simmer for 10-12 minutes until cooked to al dente, stirring occasionally. Remove the bay leaves.
5. Stir in the grated Parmesan and cook over a low heat for 2-3 minutes.
6. To serve, preheat the grill to a high heat. Ladle the soup into bread bowls and top with the grated Mozzarella. Place on a baking tray and place under the hot grill for 3-4 minutes until the cheese is bubbly and melted. 
7. Remove from the oven and garnish with chopped fresh basil and serve.

Per serving: 689kcals, 22.3g fat (8.7g saturated), 70.5g carbs (10.6g sugars), 46.5g protein, 3.7g fibre, 1.249g sodium