Idli is the steamed rice-and-lentil cake at the center of South Indian tiffin: soft, white, faintly sour, and almost weightless when it is made well. It is a fermented food before it is a steamed one, and that is the whole point of it. A batter of rice and split black gram is left to ferment overnight, then portioned into shallow moulds and steamed into pillowy discs, served hot with sambar and chutney. It is breakfast, it is a light meal, it is the gentlest thing on a tiffin menu, and its quality is judged almost entirely on texture.
The make is short to describe and easy to get wrong. Rice and urad dal are soaked separately, ground separately, the dal to a light aerated paste, then combined with salt and left to ferment until the batter rises and smells pleasantly sour. The risen batter is spooned into greased idli moulds and steamed, not boiled, for roughly ten to fifteen minutes until set and springy, then unmoulded and served immediately with sambar and a coconut or tomato chutney. Good execution gives an idli that is white, domed, spongy, and springs back when pressed, with a clean mild tang and no raw bite. Sloppy versions are dense and rubbery from underfermented or overground batter, flat and gummy from a steamer run too hot or too long, sour and sharp from batter left too far past its peak, or dry and tight from sitting around after steaming, since an idli is at its best within minutes of leaving the steamer.
Variations stay within the steamed-cake idea rather than leaving it. Rava idli swaps fermented batter for a quick semolina mix and skips the overnight wait, trading a little of the airy sourness for speed. Mini idli dunked in sambar, button idli tossed in a tempered spice oil, and idli studded with carrot or pepper are common menu turns. Day-old idli is rarely wasted: cut up and tossed with mustard seeds, curry leaves, and chili, it becomes a fried snack in its own right. The pairing with vada into a combination plate, idli vada, is its own thing and deserves its own article rather than being crowded in here.