Whisk dhania powder, haldi and salt with the buttermilk until combined.

Add the chopped cilantro, curry leaves, and green chillies and stir. Transfer to a heavy saucepan and heat on medium while stirring constantly. Continue to cook until the mixture thickens and comes to a rolling boil.

Take the saucepan off the heat while you make the seasoning as follows. Heat the vegetable oil in a small kadhai (or saucepan). Add the mustard seeds and cover, until they stop popping. Pour over the prepared majjige huli.

Serve with rice, or with rotis.