Grease a 9” round pie tin and line with baking parchment. Preheat the oven to 400°F. Mix together your meatball ingredients with your hand (apart from the tomato sauce) until well combined. Form into small meatballs. Fry in a little olive oil on all sides until nicely browned, then add your tomato sauce and cook for 5 minutes to reduce the sauce. Set aside and leave to cool.
In a large bowl, add your spaghetti, parmesan, diced mozzarella, whisked egg, meatballs and half the accompanying sauce. Mix well then tip into your pie dish. Bake for 20 minutes. Bring out and leave to cool slightly.
Turn out onto a lined baking tray. Top with remaining meatball sauce, sliced mozzarella and pepperoni. Drizzle with a little olive oil and broil for 5 minutes.
Bring out, slice up, get stuck in!