Preheat your oven to 400°F (200°C). Prick the sweet potatoes with a fork and place them on a baking sheet. Bake for about 45 minutes, or until they are tender and the skin is slightly caramelized. Let them cool for a few minutes before handling.

Once cooled, cut the sweet potatoes in half and scoop the flesh into a mixing bowl. Mash until smooth and free of lumps. You should have about 1 ½ cups of sweet potato puree.

Add the beaten egg, salt, and nutmeg (if using) to the sweet potato. Gradually incorporate the flour, mixing until a shaggy dough forms. Avoid overworking the dough; it should be soft but not sticky.

Dust a clean surface with flour and turn the dough out. Divide it into four sections. Roll each section into a rope about ¾ inch thick. Cut the rope into 1-inch pieces.

Using a fork, gently press down on each piece to create the classic gnocchi ridges. This step helps the sauce cling to the gnocchi.

Bring a large pot of salted water to a boil. Drop the gnocchi into the pot in batches. They are done when they float to the surface, which should take about 2-3 minutes. Remove with a slotted spoon and set aside.

In a skillet, melt butter over medium heat and add fresh sage if desired. Add the cooked gnocchi and toss gently to coat. Serve warm, garnished with grated Parmesan if you like.