Grind all the chutney ingredients apart from the ones for tempering together to a fine paste using water as and when required. To grind a chutney, I first grind the ingredients roughly without water and then slowly add more water. It helps in a smoother and even grinding.
In a tadka pan, heat the oil and mustard seeds, once they splutter. Add urad dal, dry red chillies and curry leaves and saute till the dal turns brown. Pour over the chutney and serve with hot idlis or crisp dosas.