First, cook your pasta according to the packaging instructions until al dente, reserving 1 cup of pasta water before draining.
While the pasta is cooking, melt 4 tablespoons of butter in a large pan at medium heat, then add the 4 minced garlic cloves, and 5 finely chopped sage leaves. Cook for 30 seconds to 1 minute until fragrant.
Add in the 2 & 1/2 cups heavy cream, 1 cup pure pumpkin, and 1/8 teaspoon of nutmeg.
Let simmer, stirring occasionally, until thickened. Then stir in the 1 & 1/2 cups grated parmesan.
Stir in the drained al dente cooked fettucini pasta and add salt and pepper to taste. If needed, add some of the reserved pasta water to thin the sauce, 1/4 cup at a time.