Soak 2 cups idli rice and 1 cup urad dal separately for 4–6 hours
Grind urad dal to a smooth, fluffy batter
Grind rice to a slightly coarse batter
Mix both batters with salt
Ferment the batter overnight or until doubled in volume
Grease small bowls, cups, or steel plates with oil
Pour the batter into the greased containers
Use a large pot, pressure cooker, or deep pan with a stand or plate inside
Add water to the bottom and bring it to a boil
Place the batter-filled containers on the stand or plate
Cover with a lid without the whistle if using a pressure cooker
Steam for 10–15 minutes on medium heat
Check with a toothpick; if it comes out clean, the idlis are done
Let them cool slightly
Remove the idlis with a spoon or knife
Serve hot with chutney or sambar