Heat the oven to 200°C/400°F. Put the squash quarters on a baking sheet and drizzle with olive oil. Place in the oven and cook for 40 minutes until soft. Leave to cool for a few minutes then blend in a food processor until smooth.
Put a pot of salted water on to get to a boil. Cook the pasta according to packet instructions.
Melt the butter over a medium heat and add the rosemary sprigs. Cook gently for 5 minutes until the butter has browned slightly then remove the rosemary and set aside. Add the squash puree, crème fraiche, nutmeg, cinnamon and chilli flakes. Season with salt and pepper. Turn the heat to low to keep the sauce warm while the pasta finishes cooking. If the sauce is too thick then you can thin it slightly with extra crème fraiche or some vegetable stock.
Add the pasta to the sauce along with the spinach and toss well to coat. Serve topped with grated parmesan.
Nutrition information is an estimate and will vary depending on the ingredients used.