While pasta is cooking, brown sausage and onion over medium heat in a large skillet. Drain off any fat. Add garlic and cook for a couple minutes. Add water, chicken base, pumpkin, spices, and salt and pepper. Simmer, uncovered, for 10-15 minutes, or till most of the liquid is reduced.
Stir in half & half and Parmesan cheese. Cook and stir till cheese is melted.
Stir in the hot pasta and serve with additional Parmesan cheese if desired.