Wash and soak udad dal in water for 5 to 6 hours.
Wash and soak idli rava for 2 hours. Soak poha for 20 minutes.
Drain the water from udad dal. Blend udad dal and soaked poha into a fine paste using little water.
In a deep vessel, add udad dal paste.
Squeeze out the water from idli rava and add to udad dal batter. Add salt and mix well . Keep aside for 8 hours for fermentation.
After 8 hours,the batter would be fermented.
Grease the idli moulds with oil.
Pour the idli batter into the idli moulds.
Boil water in a steamer/idli cooker.
Place the idli plates in the cooker.
Cook covered for 15 to 20 minutes or till the idlis are cooked.
Unmould the idlis and serve hot with chutney and/or sambar.