1. Add an appropriate amount of tapioca starch to boiling water and stir flocculent.
2. Knead into a smooth dough and let it sit for ten minutes.
3. Sprinkle a small amount of tapioca starch on the cutting board and roll the dough into a rectangular shape.
4. Spread the steamed mashed sweet potatoes evenly on the dough.
5. Roll up from bottom to top.
6. Integer and cut into small pieces evenly.
7. Put it in a greased steamer or a greased dish.
8. Steam for 15 minutes.
