Preheat your oven to 400°F (200°C).
Halve and seed the butternut squash, roast until tender, then scoop out the flesh and puree until smooth.
In a bowl, mix the squash puree with maple syrup, salt, and nutmeg.
Cook the jumbo pasta shells in boiling water until al dente, drain, and set aside.
In a saucepan, melt butter and whisk in the heavy cream, garlic powder, sage, and rosemary, thickening slightly over medium heat.
Stir in half of the parmesan cheese until melted and smooth.
Spoon the squash mixture into each cooked shell and place them into a baking dish.
Pour the cream sauce over the stuffed shells and sprinkle with the remaining parmesan.
Bake for 15-20 minutes until the sauce is bubbly and the top is lightly golden.
Garnish with fresh sage leaves before serving.