Fill a large pan with water, add a pinch of salt and bring to the boil over high heat.
Add 450g fusilli and cook until just tender (al dente) according to the packet instructions. Before draining, ladle off about 120ml of the cooking water, then drain and set the pasta aside.
Heat 1 tablespoon of olive oil in a large frying pan over medium–high heat.
Add 450g Italian sausage meat and cook, breaking it up with a spoon, until browned and cooked through (about 5–7 minutes). Transfer the sausage to a plate, leaving the fat in the pan.
Reduce the heat to medium. Add 1 large chopped onion and 2 chopped capsicums, then fry for 5–7 minutes until softened.
Add 3 minced garlic cloves and cook for 1 minute until fragrant.
Pour in 800g tinned chopped tomatoes and 120ml chicken stock. Season with ½ teaspoon of salt and ¼ teaspoon of black pepper. Bring to a gentle simmer, then cover and cook on low for 10 minutes, stirring in reserved pasta water if needed to thin the sauce.
Return the pasta and sausage to the pan. Stir in 50g grated Parmesan cheese and 15g chopped fresh basil until the pasta is well coated and heated through. Taste and adjust the seasoning.
Serve immediately, topped with extra grated Parmesan and a few basil leaves.