Preheat the oven to 200ºC/gas mark 6. Spread the butternut squash out in a small roasting tin and roast for 20-25 minutes until tender.
Meanwhile, cook the pasta according to instructions on the packet. Heat the oil in a small frying pan and fry the onion and garlic over a medium heat for 6-7 minutes until softened.
Place in a bowl with the roasted butternut squash and 65g of the cheese. Use a stick blender to purée everything, adding 150ml of water to loosen the mixture.
Drain the pasta and stir into the purée. Transfer to a shallow 20cm-square ovenproof dish and scatter over the remaining cheese. Bake in the oven for 10-15 minutes until golden and bubbling. Garnish with the chopped parsley and serve with the rocket leaves.