Remove the tough and fibrous parts of the chwinamul stems, and discard the stems.
Bring water to a boil, add salt, then put in the chwinamul. Press down so the greens are submerged in hot water (once it starts boiling again, flip them over once).
After flipping, boil for 1 more minute (to soften the tough texture, boil for a total of 1 minute).
Rinse under cold water to cool down and gently squeeze out excess water by hand (just enough so it doesn't drip).
Loosen the greens so they're not clumped together and cut into bite-sized pieces.
Break up any remaining clumps.