Preheat oven to 375 F.
Cook the pasta 1 minute short of the directions on the package and allow to cool just until you can handle it.
In a high speed blender, puree the cashews until grainy, then add in the milk, lemon and butternut squash and puree until very smooth. Transfer to a large bowl.
In a large nonstick skillet, add the olive oil along with the garlic and sage. Saute until fragrant, about 30 seconds, then add in the spinach until it wilts. Transfer to the main bowl.
Mix in 1 cup of the cheese, and season with salt, pepper, cinnamon and nutmeg.
Transfer the filling to a piping bag and fill the shells with the filling. Place in a greased 13x9" baking dish and top with the shredded remaining cheese. Bake for 20-25 minutes until bubbling and golden.
Meanwhile, to make the sauce, puree the cashews until grainy, then add in the milk and lemon and puree until smooth.
Heat the oil in the skillet over medium heat and add the garlic and sage for the sauce. Once fragrant, reduce the heat to medium low and add in the cashew liquid, maple, and season with salt, pepper, cinnamon and nutmeg. Simmer just until warm.
Serve the hot shells with the sauce and enjoy.