1. Put the steamed bread in a basin, cover it with cloth and put it in a warm and humid place (cool place). After about a week, the yellow enzyme bacteria will grow.

2. Crush the steamed bread, add salt, and mix with appropriate amount of water and stir evenly.

3. Put the basin in the sun for about two weeks to make yellow noodle sauce.

Note: Don't forget to stir the sauce up and down frequently.