1. Ingredients: appropriate amount of black beans and appropriate amount of mature vinegar.

2. Wash the black beans, dry them and set aside.

3. Put in a wok and stir-fry over medium-low heat for about 10 minutes.

4. Stir-fry the black beans until the skin bursts, then reduce the heat to low and stir-fry for about 5 minutes.

5. Turn off the heat and let the black beans cool.

6. Put the black beans into a glass bottle with a lid, pour vinegar over the black beans, cover, seal, and store in the refrigerator or a dark place. The black beans can be eaten after they absorb the vinegar and swell.