1. 1. Start the Pasta Water: Bring a large pot of salted water to a rolling boil. Add the fettuccine and cook according to package directions until al dente. Reserve about 1 cup of the pasta cooking water before draining the pasta.

2. 2. Saute Aromatics: While the pasta cooks, melt the butter in a large skillet or Dutch oven over medium heat. Add the finely diced onion and cook until softened and translucent, about 5-7 minutes. Stir in the minced garlic and cook for another minute until fragrant, being careful not to burn it.

3. 3. Whisk in Pumpkin and Liquids: Pour in the pumpkin puree, heavy cream, and milk into the skillet. Whisk everything together until smooth and well combined. Bring the mixture to a gentle simmer, stirring occasionally.

4. 4. Season the Sauce: Reduce the heat to low. Stir in the dried sage and nutmeg. Season generously with salt and freshly ground black pepper to taste. Continue to simmer gently for about 5-7 minutes, allowing the sauce to thicken slightly.

5. 5. Add the Cheese: Gradually stir in the grated Parmesan cheese, a handful at a time, until it’s fully melted and incorporated into the sauce. The sauce should become smooth and velvety. If the sauce seems too thick, add a splash of the reserved pasta water until it reaches your desired consistency.

6. 6. Combine Pasta and Sauce: Add the drained fettuccine directly into the skillet with the pumpkin alfredo sauce. Toss gently to coat all the pasta evenly. If needed, add a little more reserved pasta water to achieve a perfectly creamy coating.

7. 7. Serve Immediately: Garnish with fresh chopped parsley and a sprinkle of extra Parmesan cheese, if desired. Serve hot and enjoy your cozy fall dinner!