Two cups rice, one cup urad dal (split black gram), 1/4 cup poha (flattened rice), salt to taste, water as needed, and oil for greasing.
Wash the rice, urad dal, and poha, separately. Soak the rice and urad dal in water for 4-6 hours. Soak the poha for about 30 minutes before grinding.
After draining the water from the urad dal, grind it into a smooth and fluffy batter by adding water as needed. Separately, grind the rice into a slightly coarse batter. Mix both batters in a large bowl. Lastly, add the soaked poha and grind to a smooth paste. The consistency should be thick but pourable.
Cover the batter and let it ferment in a warm place for 8–12 hours or overnight. The batter should rise and become slightly bubbly.
Grease thatte idli plates with oil. You can even use the small steel plates you have at home. Pour the fermented batter into the plates, filling them halfway.
Place the idli plates in a steamer and steam for about 15–20 minutes on medium heat. To check if they're done, insert a toothpick or knife in the centre; it should come out clean.
Let the idlis cool slightly before removing them from the plates. Serve hot with coconut chutney, sambar, or your favourite side dish.