To Make the Idli Batter: For every three cups of Idli Rava, you have to use one cup of urad dal washed. Soak the idli rava and urad dal separately for about 6 hours. Only the urad dal has to be ground to a smooth paste and the soaked Idli Rava is mixed with this. Add salt and mix. Leave the batter to ferment overnight. Use this batter to steam your idlis in a pressure cooker for soft and fluffy idlis every time!