The leaves are deliberately left to ferment for about a week before they're sun-dried, and by the time they're ready, they've lost most of their green color along with roughly 90 percent of their original carotenoids.
Mustard, radish, or cauliflower greens are packed tight and left to ferment for roughly a week, then spread out to dry in the sun until dark and pungent. Southern Bhutan's Nepali-descended Lhotshampa households simmer it into a sour soup or fry it as a side, eaten alongside rice and lentils.