Heat the oven to 200℃/180℃ Fan/400℉.
Cut the 1 kg (2lb) butternut squash in half and scoop out the seeds. Brush the cut edge of the squash with oil and place cut side down on a roasting tin.
Roast in the oven for about 30 minutes or until the squash is soft all the way through.
While the squash is roasting, peel the skin off 225 grams (1½ cups) chorizo and cut into small dice (1-2 cm/¼ in)
Heat a frying pan to medium and put the chorizo into the pan until the chorizo pieces are slightly crispy round the edges, keep them moving so they don't burn. Once cooked take off the heat.
Cook 200 grams (1 cup) macaroni according to the packet instructions.
Once the squash has cooked remove it from the oven and scoop out the soft flesh straight into your blender or food processor.
Add 200 ml (1 cup) milk, 100 grams (1 cup) cheese and 1 teaspoon of butter. Process until all the ingredients are blended and you have a thick sauce, if it is too thick add a little more milk.
Drain the pasta and mix with the chorizo, including the oil from the pan, and the butternut squash sauce. Season with 1 teaspoon of salt and ½ teaspoon of freshly ground black pepper, taste and adjust the seasoning to your taste.
You can serve the macaroni immediately but I prefer to put it into an ovenproof dish, cover with 50 grams (½ cup) grated cheese and bake at (200℃/180℃ Fan/400℉) for 15 minutes.
Or you can prepare the dish to this stage and reheat from cold at 160℃/150℃ Fan/ 325℉ for 30-40 minutes.
Serve warm with a side salad or a simply cooked green vegetable such as broccoli or green beans.