Preheat your oven to 375°F (190°C).

Bring salted water to a rolling boil and cook the jumbo pasta shells for 8-10 minutes until al dente. Drain and rinse under cold water.

In a mixing bowl, combine pumpkin puree, ricotta, half of the mozzarella, Parmesan, garlic powder, sage, nutmeg, salt, pepper, and the egg until smooth.

Spread 1 cup of marinara sauce in the bottom of a 9x13-inch baking dish.

Fill each pasta shell with the filling and place them in the baking dish with the open side up.

Pour the remaining marinara sauce over the shells and sprinkle with the rest of the mozzarella.

Drizzle olive oil on top and cover with aluminum foil. Bake for 25 minutes.

Remove the foil and bake for an additional 10 minutes until the cheese is bubbly and golden brown.

Let the dish rest for about 5 minutes before serving.

Serve warm, optionally garnishing with parsley or sage.