Begin by bringing a large pot of salted water to a rolling boil. Add the jumbo pasta shells and cook them for about 9-11 minutes, or until they are al dente. Once cooked, drain the shells in a colander and rinse them gently under cold water to stop the cooking process. Allow them to cool while you prepare the filling.

In a spacious mixing bowl, combine the canned pumpkin puree, ricotta cheese, and smoked Gouda cheese. Season the mixture with salt, pepper, and chopped fresh sage for aromatic flavor. Stir everything together until well blended, ensuring a creamy consistency.

Preheat your oven to 350°F (175°C). Using a teaspoon or a piping bag, carefully fill each pasta shell with the creamy pumpkin and Gouda filling, ensuring they are well-stuffed but not overflowing.

In a medium saucepan, melt the unsalted butter over medium heat. Keep an eye on it as it cooks, stirring frequently, until it turns golden brown and emits a nutty aroma, about 4-5 minutes. Remove from heat and immediately stir in the heavy cream, Parmesan cheese, salt, and pepper.

Pour half of the brown butter sauce evenly over the stuffed shells in the baking dish. Sprinkle the remaining smoked Gouda on top, ensuring the cheesy goodness seeps into every nook and cranny. Drizzle a bit more of the sauce on the shells.

Carefully place the baking dish in the preheated oven and bake for 25-30 minutes, or until the stuffed shells are heated through and bubbly. Once done, drizzle the reserved brown butter sauce over the top before serving.