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 1/2 cup of the starchy pasta water. Drain the pasta, drizzle with 1 tbsp olive oil to prevent sticking, and set aside.

While the pasta cooks, heat a small, dry skillet over medium-low heat. Add the pecan halves/pieces and toast for 3-5 minutes, stirring frequently, until fragrant and lightly browned. Be careful not to burn them. Remove from heat and set aside.

In a large skillet or Dutch oven, melt 2 tbsp butter with 1 tbsp olive oil over medium heat. Add the chopped onion and cook for 5-7 minutes, until softened and translucent. Add the minced garlic and chopped fresh sage, cooking for another 1-2 minutes until fragrant.

Stir in the pumpkin puree, vegetable broth, nutmeg, salt, and black pepper. Bring the mixture to a gentle simmer, then reduce heat to low and cook for 5 minutes, allowing the flavors to meld.

For an even smoother sauce, carefully transfer the mixture to a blender or use an immersion blender directly in the skillet. Blend until completely smooth. (Optional step, but highly recommended for a luxurious texture).

Return the sauce to the skillet (if transferred). Stir in the heavy cream and grated Parmesan cheese. Cook for 2-3 minutes, stirring constantly, until the cheese is melted and the sauce is heated through and slightly thickened. Taste and adjust seasonings as needed.

Add the drained pasta to the skillet with the pumpkin sage sauce. Toss gently to coat the pasta evenly. If the sauce is too thick, add a splash or two of the reserved pasta water until it reaches your desired consistency.

Serve immediately, garnished with the toasted pecans, extra fresh sage leaves, and a sprinkle of additional grated Parmesan cheese.