Preheat oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.

Cook jumbo pasta shells in a large pot of boiling salted water until al dente; drain and set aside to cool.

In a medium mixing bowl, combine the pumpkin puree, ricotta cheese, 1 cup of shredded Gouda, the egg, 0.25 cup of Parmesan, nutmeg, salt, and pepper.

In a medium saucepan over medium heat, melt the butter and cook until it begins to brown and smells nutty, approximately 5-7 minutes.

Add the fresh sage leaves to the brown butter and fry for 1 minute until crisp; remove the sage leaves with a slotted spoon and set aside.

Add the minced garlic to the brown butter and cook for 30 seconds, then slowly whisk in the heavy cream.

Simmer the sauce over medium-low heat for 5 minutes until thickened, then stir in the remaining 0.25 cup of Parmesan cheese.

Spread 0.5 cup of the prepared sauce onto the bottom of the baking dish.

Stuff each cooked shell with approximately 2 tablespoons of the pumpkin mixture and arrange them in the baking dish.

Pour the remaining alfredo sauce over the stuffed shells and sprinkle with the remaining 1 cup of Gouda.

Bake for 20 to 25 minutes until the cheese is melted and the sauce is bubbling.

Garnish with the fried sage leaves before serving.