Gundruk is fermented green vegetable (leaves). Allow mustard, turnip, radish, cauliflower, etc leaves to wilt for one or two days and then shred (unevenly cut into small pieces). You can use Sometimes roots of the plants too, but not all the plants, raddish or turnip, etc. You can mix roots of radish with the leaves and smashed together. Don' make it too small while smashing.
Put those smashed stuffs into a wooden, earthenware or in glassjar very compressed. Close tightly the mouth of the container. Put it in safe and sunny place. It may be placed in an open place. Don't check it often. After few days let's say 3 days check the acidity (sourness), you can know if it is ready from it's strong smell.
Dry it then under the sun. After few days take it off the sun and Taste it. If it taste Gundruk, you are done. Mix it in any vegetable and eat it. Don't try to cook it. You can't cook Gundruk.
Take fresh green leaves plucked from the garden
Sun dried for a day or two
Pack them tightly in a container with air-tight lid
Containers stand for a week or more until the leaves takes upon natural fermentation process due to lactic acid bacteria
After a thorough fermentation, take the whole contents of the container and spread out on a thin plastic sheet and sun-dried it fully for several days,
Then store it in containers
Gundruk is ready
II. Sinki (you can take mula or kauli - Raddish or Cauliflower)
Break or cut vegetables into small pieces and spread them in son for several days
Store it in air tight container until the leaves takes upon natural fermentation process due to lactic acid bacteria.
After a thorough fermentation take it out and spread it out in the sun and let it dry
Sinki is ready to cook.