1. Put all the ingredients except butter and purple sweet potato into the bread machine to start the kneading program
2. Add the weighed purple sweet potato and butter again and start the dough procedure to make it into a dough
3. Prove the dough to 2 times its size
4. Divide the dough into 6 equal parts
5. Take the small dough in turn and roll it out
6. Roll up the dough (you need to roll it tightly, and you can apply some water to the end of the roll to prevent the dough from falling apart)
7. Cut into two from the middle.
8. Put it in a square baking dish lined with greased paper
9. Secondary fermentation to 2 times the size
10. Put it into the preheated 200 degree oven for 12 minutes (the bread will be colored quickly, adjust the temperature according to your own oven)
11. Features: delicate taste, soft as velvet inside, crispy bottom and tender inside, milky taste
