Step 1: For the cowpea just picked from the ground, select tender and full cowpea, pick out the part with insects, and pinch off both ends without washing.

Step 2: Put the cowpea in a pot and sprinkle some salt. Don't put too much salt, just the same salt as usual. This can promote the cowpea to ferment quickly and turn sour. Too much salt will only be salty and not sour.

Step 3: Massage gently with your hands and knead well.

Step 4: Marinate for about half an hour.

Step 5: Wash the beverage bottle or oil pot with edible oil with detergent, and then rinse it with cold boiled water to prevent water from entering the bottle. The pickled cowpea softened a little and put it in a beverage bottle. Press tightly with chopsticks when loading.

Step 6: Tighten the bottle cap and marinate for one month before eating.