Put the pasta on to cook in a pot of boiling, salted water and cook to al dente.
Meanwhile, in a large nonstick pan, melt the butter over medium heat and sauté the garlic for 1 to 2 minutes. Add the sage and fry for another minute or 2, until fragrant but not browned.
To the pan, add the pumpkin puree, cream cheese, and Parmesan. Stir together until smooth, then whisk in the milk until fully incorporated.
Continue cooking until the Parmesan has melted, stirring occasionally. Season the sauce with salt and pepper.
Once the pasta is cooked, drain and reserve 1 cup of pasta cooking water, then add the pasta to the sauce and stir to fully coat the noodles. Add pasta cooking water as needed to loosen up the sauce if it’s too thick.