Bring a large pot of salted water to a boil, then add the pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain and set aside.
Meanwhile, melt the butter in a large skillet over medium heat. Add the minced garlic and cook for about 30 seconds until fragrant and just starting to turn golden, filling your kitchen with a warm aroma.
Add the pumpkin puree to the skillet with the garlic, stirring well to combine. Let it cook for 2 minutes, which helps to warm the puree and meld the flavors, and note the vibrant orange color intensify slightly.
Pour in the heavy cream, stirring continuously. Bring the mixture to a gentle simmer and cook for 3-4 minutes, allowing the sauce to thicken slightly and develop a rich, velvety texture.
Stir in the grated Parmesan cheese, a pinch of nutmeg, and season with salt and pepper to taste. Continue stirring until the cheese melts and the sauce becomes smooth and glossy, with a warm, inviting color.
Add the drained pasta to the skillet, tossing gently to coat each piece with the luscious pumpkin sauce. If the sauce appears too thick, add a splash of reserved pasta water to loosen it until it reaches your desired creaminess.
Cook everything together for another 2 minutes, allowing the flavors to meld and the pasta to absorb some of the sauce’s richness. The sauce should cling beautifully to each strand or piece of pasta.
While the pasta finishes cooking, crisp the sage leaves in a small pan or microwave until fragrant and crispy, then crumble or leave whole for garnishing.
Serve the pumpkin Alfredo hot, garnished with grated Parmesan and crispy sage leaves for a delightful aroma and texture contrast. Enjoy the vibrant color and creamy consistency of this cozy fall dish.