Soak urad daal for about 3-4 hrs ,at the same time mix the idli rava with water and let the consistency be thick.
Now blend the urad daal till its soft and fluffy.
Add idli rawa to the blended urad daal and mix it well to prepare batter.
Place the mixture in a warm place for 8-10 hours or overnight to let the mixture ferment.
In winter, you can place it in oven (switched off).
Add salt and inch of soda before making.
Grease the idli maker plates with oil and fill it with batter.
Heat water in the idlimaker pan and place the filled idli plates and cover it with lid.
Steam it in high for about 15-20 minutes.
Remove the idlis from the plates.
Serve hot with sambar ,coconut chutney or any other chutney.