Blanch the bathua leaves in boiling water for about 3-4 minutes.
Drain and put in chilled water immediately so that it stops cooking further, this also keeps the leaves bright and green.
Using the hand blender give the leaves a quick blend, don't make a paste out of it though.
Whisk the curd well and keep aside.
Heat the oil in a small pan and add hing to it, after a minute add mustard and jeera seeds. Once they start to crackle, add the green chillies and fry for a minute.
Add bathua and salt to the whisked curd and top with the tadka.
Served chilled, I like making it and serving after an hour, the flavours blend beautifully in that time.
Notes
PS: Read a fabulous piece on bathua by Chef Manu Chandra here