Drain them and grind it into a smooth batter with less amount of water as we do for regular Idli batter till it is fluffy. The batter should not be too watery, as it will result in the Idlis becoming very thin.
Add salt to taste and allow the batter to ferment for 6 to 8 hours.
Heat the ghee in a frying pan and add black pepper and cumin seeds and fry for a few seconds.
Take them out of the pan and grind them into a coarse powder and add it to the Idli batter.