Rinse ½ cup of urad dal and 1 cup of idli rice separately, and soak each in water for at least 6 hours. For the last 30 minutes, also soak 2 tablespoons of thick poha (flattened rice) in water.
Drain the dal and blend it with the soaked poha, ½ teaspoon of non-iodized salt, and a little chilled water to a thick, smooth, frothy batter.
Drain the rice, grind it with a little water until slightly coarse, and mix it into the dal batter.
Cover and leave in a warm place for 8-14 hours, until the batter rises and doubles.
Pour the batter into greased idli molds and steam, covered, over high heat for 10 minutes.
