Pickled mustard greens

Pickled mustard greens are a popular dish in Hmong cuisine. In Laotian it’s called som pak. The dish is traditionally made by putting fresh mustard greens into a container, typically a large pot, along with rice water, chillies, salt, and other spices if desired. The pot is then left usually at room temperature or in a sunny spot to ferment. After a few days, the pickled mustard is ready to eat. In modern practice, vinegar is sometimes added to the mixture to speed up the preparation of the dish.
"Pickled mustard greens" is a common dish across East and Southeast Asia, although the English phrase is non-specific. In China there is xuě cài, made with a leafy mustard variety called xuě lǐ hóng, and in Southern China haam choy, made with gai choy mustard leaf. Japanese pickled mustard greens are called takanazuke, which is marinated in vinegar, sugar, salt, and an umami soy-based sauce.