Steps:

1. Wash prunes and put them in a container. Add water to prunes and soak them in two spoonfuls of salt for 2-3 hours to remove the astringency of prunes.

2. Peel and core the soaked plums.

3. Put the green plums in a bowl, add 250g of rock sugar and steam for 40 minutes.

4. Pour the steamed plums into a small pot, heat them on low heat, and stir for 3-5 minutes while cooking.

5. After the plum sauce is out of the pot, put it in a sealable container and put it in the refrigerator for refrigeration.