Preheat the oven to 400°F. Butter a 2-quart casserole dish with 1 tablespoon butter.
Cook the pasta according to package directions. Drain. Add the shells to the buttered casserole dish with the cubes of mozzarella.
In a bowl, mix the pumpkin, heavy cream, shallots, 1 teaspoon garlic powder, thyme, nutmeg, and season with salt, pepper, and chili flakes. Whisk in the parmesan.
Evenly pour the pumpkin sauce over the shells. Top with Gouda cheese. Sprinkle with the remaining garlic powder and the sage. Add the prosciutto and 3 tablespoons of butter.
Bake 30 minutes, until the cheese is browning.
Top with fresh chopped parsley or basil. Scoop and enjoy!
