Preheat your oven to 375°F (190°C).

In a large pot, bring salted water to a boil and add 1 lb. of dry tubular pasta. Cook until just under al dente, about 2 minutes shy of package instructions.

In a skillet, melt 2 tablespoons of butter over medium heat. Add ½ cup of finely chopped walnuts and 2 tablespoons of fresh sage. Sauté for about 5 minutes until fragrant.

In the same skillet, add 2 tablespoons of olive oil and sauté 1 finely chopped yellow onion along with 8 oz. of sliced cremini mushrooms for 7-8 minutes until onions are translucent.

Stir in ¼ cup of tomato paste, 4 minced garlic cloves, and ½ teaspoon of crushed red pepper flakes. Cook for 4-5 minutes until tomato paste caramelizes slightly.

Add 3-4 handfuls of fresh baby spinach and cook until wilted, about 2-3 minutes. Season with 1 teaspoon each of dried oregano and kosher salt, ½ teaspoon of black pepper, and ¼ teaspoon of ground nutmeg.

Stir in 3 cups of vegetable broth, along with 1 can of pumpkin puree, ½ cup of grated Parmesan cheese, and 1½ cups of divided grated Fontina cheese. Cook until cheeses are fully melted.

In a large mixing bowl, combine the cooked pasta with the pumpkin sauce and transfer the mixture into a greased 13x9-inch baking dish.

Sprinkle the remaining ½ cup of grated Fontina cheese and the walnut-sage mixture on top. Cover with foil and bake for 15 minutes.

Uncover and return the dish to the oven for an additional 10-15 minutes until the cheese is melted and golden brown.