1. The purple sweet potato is steamed, cut into pieces and mashed.
2. Yeast is dissolved in warm water.
3. The purple sweet potato is mixed with flour, white sugar, yeast water and made into a Sanguang dough.
4. The remaining flour and yeast white sugar are combined into a Sanguang white dough. The two types of dough are fermented in a warm place.
5. Make the custard filling while fermenting the dough.
6. Take out the dough when you smell the wine.
7. Knead out air in both doughs.
8. Roll the two pieces of dough into square slices and stack them up from one end to form a cylindrical shape.
9. Use a knife to cut the cylindrical surface into small doses. Roll each portion into thin slices.
10. Place the custard filling in the middle of the dough and wrap it up.
11. Use the method of buns to close the mouth and round it. Put the whole dough in the steamer for the second proofing for 30 minutes.
12. Just steam it in a steamer.
