Soak urad dal and poha in 1 ½ cup water for 4 hours.
Grind the soaked ingredients in to a fine paste and transfer in to a big bowl.
Add to this paste ragi flour and salt and mix well. Add water so that the batter is not too thick or too thin.
Cover the bowl and let it ferment overnight or minimum for 6 hours.
When ready to prepare Idlis, grease the idli moulds.
Stir the batter well and pour a spoon full in the mould.
Steam the Idlis for 12 to 15 minutes.
Once cooked, cool and serve with hot sambhar and coconut chutney.