Wash the urad dal in running water. Soak it in sufficient water for 4-5 hours

Soak idli rava in water for 30-45 minutes

Once the urad dal is soaked, grind it into a very smooth batter by adding little water

Transfer into a large bowl. Fluff the batter using your hand to incorporate some air

Squeeze out the water from idli rave and add it to the urad dal batter

Mix it well making sure that the dal and idli rava are completely incorporated. Use your hands to mix the batter

Cover it and set aside overnight (8 to 10 hours) in a warm place to allow the batter to ferment

The batter will ferment by next morning and air pockets will be visible on it

Scoop out the batter that you will be using immediately and add salt to it (the remaining batter can be stored in the refrigerator for 2-3 days. Make sure you add salt just before making the idlis).

Lightly grease the mould on idli plates

Spoon in batter about ¾ of the mould

Steam for 12 minutes

Serve hot