Cook the pasta according to the instructions on the packet. Drain.
Meanwhile, heat the oil in a large frying pan over a medium heat. Add the sausages and onion and cook, turning occasionally, for 3-5 minutes. Add the courgettes and continue to cook for a further 5 minutes until the onions and courgettes are golden and the sausages are cooked through. Remove the sausages from the pan and set aside to cool a little.
Stir in the chilli, passata and crème fraîche. Bring to a simmer and cook for 3 minutes until heated through.
Meanwhile, heat the grill to high. Cut each sausage into three pieces on the diagonal, then add to the pan along with the cooked pasta and parsley. Toss until combined, then tip into a 2-litre ovenproof dish. Sprinkle over the cheese and put under the grill for 3-4 minutes until golden and bubbling.