1. Prepare the materials.
2. Soak the white fungus with water in advance to soften it.
3. Peel the sweet potatoes and cut into pieces, soak them in water for 3 while.
4. The yam is peeled, washed and cut into pieces. If not, soak it in clean water immediately.
5. Soak the white fungus to remove the pedicles and wash, tear off the small flowers.
6. Put the white fungus into the pot, add some water and cook for 30 minutes.
7. Add the sweet potatoes and yam and cook for another half an hour.
8. Finally add rock sugar and boil.
