1. Preheat the oven to 240°C/220°C fan/ gas mark 9.
2. Bring a large pot of salted water to the boil over a high heat and cook the pasta for two minutes fewer than specified by package instructions or until just barely al dente. Drain the pasta, reserving 100ml of the cooking water.
3. Heat one tablespoon of the oil in a large pan over a medium-high heat and cook the meatballs for 2-3 minutes.
4. Add the peppers and cook for 5-6 minutes longer until the meatballs are browned and the peppers are starting to char.
5. To make the pesto, combine the spring onions, spinach, Parmesan, vegetable stock, most of the basil and the remaining olive oil in a food processor and whizz until smooth. Season to taste.
6. Return the drained pasta to the saucepan. Stir in the pesto, reserved cooking water, meatballs and peppers.
7. Transfer to an ovenproof dish and top with the mozzarella. Bake for 15 minutes or until golden. Season with black pepper and scatter with some extra fresh basil.

Per serving: 700kcals, 29.6g fat (11g saturated), 70.1g carbs (5g sugars), 43.1g protein, 7.6g fibre, 0.986g sodium