1. Boil the sweet potatoes until tender, about 15 minutes. Drain and mash until smooth.
2. In a large bowl, combine mashed sweet potatoes, flour, egg, and salt. Mix until a dough forms.
3. On a floured surface, knead the dough lightly and divide into four portions. Roll each portion into a long rope and cut into 1-inch pieces.
4. Press each piece lightly with a fork to create ridges.
5. Bring a large pot of salted water to a boil. Cook the gnocchi in batches until they float to the surface, about 2-3 minutes. Remove with a slotted spoon.