firstly, in a large bowl take 1 cup urad dal and rinse well.
soak in water for 4 hours.
after soaking for 4 hours, transfer the dal to mixi jar. you can alternatively grind in a grinder.
grind to smooth and fluffy batter adding water as required.
transfer the batter to a large bowl.
now in another bowl take 2 cups rice rava and rinse a couple of times.
squeeze off the water from the rava and transfer it to the urad dal batter bowl.
mix well using your hand. this helps to aid fermentation.
now cover and keep in a warm place for 8 hours for fermentation.
after 8 hours, the batter has well fermented. mix gently.
add 1 tsp salt and mix making sure the salt is well combined.
now to prepare the cups from banana leaf, cut the banana leaf into a round shape.
and using a stapler, pin it up into 4 sides forming a cup.
place the cup in the steamer and pour the batter into the moulds.
cover and steam for 20 minutes or until the idlis are cooked well.
finally, enjoy soft idli with chutney or sambar.