Start by rinsing the urad dal thoroughly a few times under running water. Once cleaned, soak the lentils in sufficient water for approximately 4 hours.

Rinse the idli rava once or twice and soak it in enough water separately for 4 hours.

After soaking, drain all the water from the urad dal. Reserve some of this water—it can be used during the grinding process, or you may opt for fresh water.

Drain the soaked idli rava completely. To remove excess moisture, take small portions of the rava in your palm, squeeze out the water thoroughly, and transfer the squeezed portions to a blender or mixer-grinder jar. Repeat until all the rava is squeezed and added to the blender.

Now, add the soaked urad dal and the cooked leftover rice into the same blender jar.

Begin grinding by adding 2 to 3 tablespoons of water. Grind briefly, then continue adding the remaining water gradually in batches while grinding. Avoid pouring all the water at once to prevent the batter from turning runny.

Depending on the texture and absorbency of the lentils and rava, you might need to adjust the water quantity slightly. Aim for a batter that has a medium-thick, flowing consistency—smooth, fluffy, and finely ground.

Transfer the batter into a deep bowl or pan and stir in salt according to taste.

Cover the bowl with a lid and allow the batter to ferment in a warm place for 8 to 9 hours or overnight, until it rises and develops a light, airy texture.

Once the batter has fermented, prepare your steamer or electric cooker by adding 2 to 3 cups of water. If you're using a stovetop pressure cooker, remove the vent weight (whistle) before steaming.

Switch on the heat and bring the water to a rolling boil.

Lightly grease the idli moulds with oil to ensure easy release after steaming. Pour the fermented batter into the moulds, filling them about three-fourths full.

Carefully place the idli stand or mould tray into the steamer, electric cooker, or pressure cooker. Secure the lid.

Steam the idlis for 10 to 12 minutes, or until a toothpick inserted in the center comes out clean—indicating they’re fully cooked and fluffy.

Once done, remove the moulds and let them cool for a minute before gently unmoulding the idlis.

Serve warm or piping hot with fresh coconut chutney, spicy sambar, or both for a traditional and satisfying South Indian meal.