Soak bean threads in hot tap water and mushrooms in 40-second microwaved hot tap water until soft. About 10 minutes. Drain and rinse mushrooms well.
Cut a slit along each bitter melon and remove the seeds with a spoon. Sometimes it just wont open properly so you’ll need to split the melon in half lengthwise and just add the filling.
Bring the water and broth to a boil in a pot on high heat, but put aside about 1 cup for adjusting seasoning.
Add the stuffed bitter melons
Turn heat down to reach a low boil, simmer for 20-30 minutes until bitter melons are fork-tender.
The water will have slightly evaporated and the stuffing released seasoning to the broth, so taste it then add salt and sugar to your liking if needed, or add more hot water to dilute it.
Remove bitter melons and cut into 1.5-2″ long pieces.
Garnish with cilantro and green onion, serve with broth.