Preheat the oven to 180 degrees C. Bake sweet potatoes for 30 minutes, or until soft to the touch. Remove from the oven and set aside to cool.
Once the potatoes are cool enough to work with, remove the peels and mash them, or press them through a ricer into a large bowl. Blend in the garlic, salt, nutmeg and egg. Mix in the flour a little at a time until you have soft dough. Use more or less flour as needed.
Bring a large pot of lightly salted water to a boil. While you wait for the water, make the gnocchi. On a floured surface, roll the dough out in several long snakes and cut into 3cm sections. Drop the pieces into the boiling water and allow them to cook until they float to the surface. Remove the floating pieces with a slotted spoon, and keep warm in a serving dish.