1. Prepare the Crust:

1. Preheat oven to 400°F. Pierce sweet potatoes with a fork and bake for 45-50 minutes until tender. Let cool slightly, then scoop out flesh and mash until smooth.
2. In a large bowl, combine mashed sweet potatoes, flour, egg, salt, and nutmeg. Mix until a soft dough forms (add more flour if too sticky).
3. Divide dough into 4 parts. Roll each into a rope about 1-inch thick, then cut into 1-inch pieces. Press lightly with a fork to create ridges.
4. Bring a large pot of salted water to a boil. Cook gnocchi in batches for 2-3 minutes until they float to the surface. Remove with a slotted spoon.
5. In a skillet, melt butter over medium heat. Add sage leaves and cook until crisp and butter is lightly browned. Toss cooked gnocchi in the sage butter and sprinkle with Parmesan before serving.