Preheat your oven to 400°F (200°C).

Cook the jumbo pasta shells according to the package instructions until al dente, about 10-12 minutes. Drain and set aside.

In a skillet over medium heat, add olive oil and sauté half of the chopped fresh sage with the diced yellow onion until translucent, about 3-5 minutes.

Combine ricotta cheese, pumpkin puree, 1/3 cup gouda, minced garlic, and nutmeg in a bowl. Season with salt and pepper and fold in the sautéed onion and sage.

In a saucepan, melt unsalted butter over medium heat until golden brown. Add remaining sage, then whisk in flour to form a roux. Gradually add heavy cream, whisking until thickened.

Spread half of the prepared alfredo sauce in a baking dish. Fill pasta shells with the pumpkin gouda mixture and place them seam-side up in the dish.

Pour remaining alfredo sauce over the stuffed shells and sprinkle with leftover gouda cheese.

Bake in the preheated oven for 20-25 minutes until the cheese is bubbly and golden.

Let the shells rest for a few minutes before serving. Garnish with crispy fried sage leaves and freshly cracked black pepper.