Arrange the pumpkin chunks on a baking sheet, drizzle with a little olive oil, and roast in a preheated oven at 200°C (390°F) for 25-30 minutes until deeply caramelized and tender.
While the pumpkin roasts, cook the pasta in a large pot of salted boiling water until just al dente, about 8 minutes. Reserve a cup of pasta water before draining.
In a skillet, melt the butter over medium heat and add the minced garlic. Cook until fragrant, about 1 minute; the garlic should be aromatic and slightly golden.
Add the roasted pumpkin to the skillet and mash it gently with the back of a spatula or a fork, breaking it down into smaller pieces. Pour in the heavy cream and stir to combine.
Let the mixture simmer gently for a few minutes until it thickens slightly, releasing a warm, sweet aroma. Then, stir in the grated Parmesan cheese until melted and smooth.
Add the cooked pasta to the skillet, tossing gently to coat each strand with the luscious sauce. If the sauce is too thick, loosen it with a splash of reserved pasta water until creamy and coats the pasta evenly.
Season with salt, pepper, and a pinch of nutmeg. Taste and adjust the seasoning as needed; the sauce should be richly flavored with a hint of warmth from the nutmeg.
Serve the pumpkin Alfredo hot, garnished with fresh herbs and additional Parmesan if desired. Enjoy the creamy, velvety texture and comforting fall flavors.
