Method
Soak
Rinse the mung beans and soak in cold water for 4–6 hours or overnight until plump and swollen.
Freeze (the key step)
Drain the soaked beans, transfer to a bag or bowl, and freeze for at least 2 hours until solid. The ice crystals rupture the cell walls of the bean skins — when they hit boiling water, they bloom open almost immediately.
Cook
Bring the water to a boil in a pot. Add the frozen beans directly, boil hard for 5 minutes, then reduce to a medium-low simmer. Cover and cook for 20–30 minutes until all the beans have opened up.
Sweeten
Add the rock sugar only after the beans have fully bloomed. Stir to dissolve. Serve hot or chilled.
Key Tips
- Freezing the soaked beans is the essential trick for getting every single bean to bloom — don't skip it
- Sugar must go in after blooming — adding it earlier firms up the skins and prevents them from opening
- Add all the water at the start; adding cold water mid-cook can make the beans uneven
- Keep the lid on throughout to maintain steady heat for uniform blooming
- For a clear broth, stir minimally; for a thick, starchy soup, cook longer and stir more