In a large, deep pan or skillet set over medium high heat, melt the butter.
Place the pancetta in the pan and cook until crisp then remove from the pan and set aside.
Add the onion and garlic and sauté until soft and fragrant.
Add the sage to the pan and allow to fry for a few seconds then add in the pumpkin puree and pour in the cream.
Stir together then season to taste. Reduce the heat and allow to simmer gently for 10 minutes while you cook the pasta. (You can blend the sauce with an immersion blender or stick blender if you prefer a smoother sauce.)
Bring a large pot of salted water to the boil. Add pasta of your choice and cook until al dente. Reserve 1 cup of cooking water then strain.
Add the pasta and Parmesan cheese to the pumpkin pasta sauce with a splash of the cooking water. Toss until the pasta is coated, adding more water if necessary.
Serve the pasta with crispy pancetta and fried sage (optional).