Grind the coconut, coriander, green chillies and tamarind with a little filtered water. Add salt and adjust to the chutney consistency you like.
Heat the oil in a small pan. Add the mustard seeds and let them splutter.
Add the urad dal. As it turns golden, add the broken Byadgi chilli and curry leaves.
Pour the tempering over the chutney and mix. Serve with idlis, dosas or Ragi Dose.