1. Mix all the ingredients other than the purple yam flour and knead them together into a very smooth Take 2 small 25g balls of dough, add purple potato flour and water to one of them to form a purple dough, and roll out the remaining large ball of dough into a long strip
3. Roll out the small balls of dough with both hands, overlap them and roll them up to a width of 5cm and a diameter of 3cm, and cut them into 7 slices
4. Roll out the small rounds, overlap them, roll them out again, overlap them, and roll them out flat
5. Wrap into long white dough, cut into 12 small pieces
6. Once fermented, steam for 10 minutes, simmer for 5 minutes out of the pot