In a large pot filled 3/4 full with salted water, cook the Fusilli until al dente. Reserve 1 1/2 cups of pasta water and set aside. Drain the pasta.

While pasta is cooking, heat the olive oil in a large skillet over medium heat. Stir in the garlic and cook about 1 minute (do not burn!) Stir in the pumpkin puree, 1 cup of the reserved pasta water, and whisk until the sauce is well blended and glossy. Stir in the half and half and add the remaining pasta water, if needed to thin the sauce. Season with salt, pepper, and nutmeg.

Stir the pasta into the sauce in the skillet and serve with parmesan cheese.