Add yam and sweet potato pieces into boiling water. Cover and heat over 3 to 5 minutes until it floated. Add a little rock sugars to stir until dissolved. Turn off heat and set aside.
Add half packet Li-Dan and Herba into warm or cold water. (Add some water which you prefered).
Pour Li-Dan and Herba mixture into yam-sweet potato soup. A fresh and delicious dessert is ready to be served.
If the weather is warm, you can add in some ice cubes into soup to make it cool-fresh. Remember to add in more Li-Dan and Herba to remain the taste.