Cook pasta according to package directions and reserve about 1/4 cup of the pasta water for later.
Melt butter in a large saucepan or pot over medium heat. Add minced garlic and sage and sauté for 2-3 minutes until fragrant. Add flour and stir until everything is combined.
Increase heat to medium-high and slowly whisk in the milk. Continue to whisk for 3-5 minutes until the mixture thickens.
Whisk in the pumpkin puree, then stir in the spices. Reduce heat, and stir in the parmesan cheese. Continue to stir until the mixture is smooth and creamy. Taste, and adjust spices as necessary. Here you can also add another splash or two of milk if the sauce appears too thick.
Add the cooked pasta and reserved pasta water, stirring everything together until the noodles are well-coated with sauce.
Divide into bowls and garnish with chopped sage. Serve with parmesan cheese and additional black pepper. Enjoy!