Cook the Pasta Shells:
Bring a large pot of salted water to a boil. Add the jumbo shells and cook just until al dente—about 1 minute less than the package directions. Drain and drizzle with olive oil to prevent sticking.

Make the Pumpkin Filling:
In a large bowl, combine pumpkin purée, ricotta, gouda, half of the parmesan, minced garlic, chopped sage, salt, pepper, and nutmeg. Mix until creamy and well blended. Taste and adjust seasoning if needed.

Prepare the Brown Butter Sage Alfredo Sauce:
In a skillet, melt butter over medium heat until it turns golden brown and smells nutty, about 4–5 minutes. Add chopped sage and cook for 30 seconds. Lower heat, pour in heavy cream, and whisk until smooth. Stir in remaining parmesan, then season with salt and pepper. Keep warm.

Stuff and Assemble:
Preheat oven to 375°F (190°C). Spread a thin layer of Alfredo sauce in the bottom of a baking dish. Fill each shell with about 2 tablespoons of the pumpkin mixture and arrange in the dish. Pour remaining sauce over the top and sprinkle with extra gouda or parmesan.

Bake:
Cover with foil and bake for 20 minutes. Remove foil and bake an additional 10–15 minutes, until sauce bubbles and the top is lightly golden.

Serve:
Let the shells rest for 5 minutes before serving. Garnish with extra parmesan and crisped sage leaves if desired.