1. Ingredients: appropriate amount of raw rehmannia, appropriate amount of cooked rehmannia, appropriate amount of black beans, appropriate amount of keel, appropriate amount of salt, and appropriate amount of water.

2. Soak the black beans for an hour.

3. Wash the keel and add water.

4. Rinse with cold water and set aside.

5. Soak black beans for one and a half hours.

6. Add appropriate amount of raw and cooked rehmannia.

7. Add all the ingredients.

8. Put two and a half bowls of water and simmer for 3 hours.

9. A dark piece after cooking.

10. Add appropriate amount of salt to taste.