I bring a large pot of salted water to a boil, then cook the jumbo shells just until al dente (they’ll finish cooking in the oven). After draining, I let them cool slightly so they’re easy to handle without breaking.
I heat olive oil in a skillet, sauté diced onion with half the chopped sage until translucent. In a bowl, I mix ricotta, pumpkin purée, ⅓ cup gouda, minced garlic, nutmeg, salt, pepper—and fold in the cooked onion once it’s cooled just a bit.
I melt butter over medium heat and let it foam and turn golden brown, then stir in remaining chopped sage. I whisk in the flour, then slowly add half the cream, whisking until thickened, followed by the rest of the cream. I season with salt and pepper and let it reduce until silky.
I spoon half the Alfredo into the bottom of the baking dish. Then I fill each shell with about 2 Tbsp of stuffing, placing them evenly in the dish. I pour the remaining sauce on top, sprinkle on the rest of the gouda, and bake at 400 °F (200 °C) for 20–25 minutes, until the cheese is bubbly and edges are golden.
While it bakes, I crisp extra sage leaves in butter or oil until crisp. Once baked, I top the dish with fried sage and a crack of fresh black pepper for garnish.