Preheat your oven to 400°F (200°C). On a large baking sheet, toss the cubed butternut squash with 2 tablespoons of olive oil, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper. Spread the squash in a single layer.

Roast for 25-30 minutes, or until the squash is tender and lightly caramelized. Set aside to cool slightly.

While the squash is roasting, bring a large pot of heavily salted water to a rolling boil. Add the pasta and cook according to package directions until al dente.

Before draining, reserve 1 to 1 1/2 cups of the starchy pasta water. Drain the pasta and set aside.

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the minced shallot and cook for 2-3 minutes until softened and translucent.

Add the minced garlic and chopped fresh sage to the skillet. Cook for another 1-2 minutes until fragrant, being careful not to burn the garlic.

Carefully transfer the roasted butternut squash, the sautéed shallot-garlic-sage mixture, vegetable broth (or 1 cup of reserved pasta water), heavy cream, 1/2 cup grated Parmesan cheese, grated nutmeg, and red pepper flakes (if using) to a high-speed blender or food processor.

Blend until completely smooth and creamy. Taste and adjust seasoning with salt and black pepper as needed.

Add the drained pasta back to the large skillet (or the pasta pot). Pour the creamy butternut squash sauce over the pasta. Toss gently to combine, ensuring all the pasta is coated.

If the sauce is too thick, add a splash or two of the reserved pasta water until it reaches your desired consistency. Heat gently for 1-2 minutes, stirring constantly.

Serve immediately, garnished with extra grated Parmesan cheese and a few fresh sage leaves, if desired.