Begin by soaking the dried longan and snow fungus in warm water for about 30 minutes or until they soften.
In a large pot, bring 6 cups of water to a boil. Once boiling, add the soaked longan, dried red dates, and ginkgo nuts. Allow the mixture to boil for about 10 minutes.
After the initial boil, add the soaked snow fungus to the pot. Let it simmer for an additional 15-20 minutes.
Once the soup is fragrant and all the ingredients are tender, add sugar to taste. Stir well to ensure the sugar dissolves completely.
Your Longan Tong Sui is now ready to be served! Enjoy it warm or chilled.