01 - Bring a large pot of salted water to a boil. Add dried pasta and cook according to package instructions until al dente. Reserve 1/2 cup pasta water and drain pasta.
02 - Heat 1 tablespoon olive oil in a small skillet over medium heat. Add chopped walnuts and cook, stirring frequently, for 3 to 4 minutes until golden and fragrant. Transfer to a plate and set aside.
03 - In a large skillet, melt unsalted butter with 1 tablespoon olive oil over medium heat. Add minced garlic and chopped sage, cooking for 1 to 2 minutes until aromatic.
04 - Stir in pumpkin puree, heavy cream, grated nutmeg, salt, and pepper. Simmer gently for 3 to 4 minutes, stirring occasionally.
05 - Add grated Parmesan cheese to the sauce and stir until fully melted and smooth. If the sauce is too thick, slowly add reserved pasta water until reaching the desired consistency.
06 - Add drained pasta to the skillet and toss thoroughly to coat with sauce. Heat for 1 to 2 minutes until evenly warmed.
07 - Plate immediately, garnishing each portion with toasted walnuts, extra grated Parmesan, and fresh sage leaves if desired.