Practice steps:

1. One common flour is fermented by adding yeast, and the other is fermented by adding steamed purple potato paste.

2. Knead and exhaust the fermented dough and roll it into dough pieces. Fold two dough pieces together, roll them into rolls, and cut them into steamed bread with uniform size.

3. About half an hour after waking up for the second time, put the pot in cold water, turn off the fire for 20 minutes when the pot is boiled, and turn off the pot after five minutes.