Preheat your oven to 375°F (190°C).

In a large pot, bring salted water to a boil. Add 1 pound of dry pasta and cook until just 2 minutes shy of al dente, about 7-8 minutes. Drain and set aside.

In a large sauté pan over medium heat, melt 2 tablespoons of butter. Add ½ cup walnuts and 2 tablespoons of fresh sage. Cook for about 5 minutes until golden. Remove, leaving drippings.

In the same sauté pan, add 2 tablespoons of extra-virgin olive oil, 8 ounces of cremini mushrooms, and 1 chopped yellow onion. Sauté for 7-8 minutes until onions are translucent and mushrooms are browned.

Incorporate ¼ cup of tomato paste, 4 minced garlic cloves, and ½ teaspoon of crushed red pepper flakes. Stir and cook for 2-3 minutes until fragrant.

Add 3-4 handfuls of fresh baby spinach. Stir until just wilted. Add 1 teaspoon of dried oregano, 1 teaspoon of kosher salt, ½ teaspoon of black pepper, and ¼ teaspoon of ground nutmeg.

Pour in 3 cups of vegetable broth. Stir in 15 ounces of pumpkin purée, ½ cup of Parmesan, and half of the 1½ cups fontina cheese. Mix until smooth.

Gently mix the cooked pasta into the pumpkin sauce until well coated.

Transfer the mixture to a greased 13x9-inch baking dish. Top with remaining fontina cheese and walnut-sage mixture.

Cover with foil and bake for 15 minutes. Remove foil and bake for an additional 10-15 minutes until cheese is melted and golden.