Before You Start
On paper idli is trivial, being rice, lentils and steam. In practice it has a name for being unforgiving, because everything that matters about it is settled hours before cooking, while the batter ferments in the dark and cannot be corrected. At its best the cake is soft, lightly sour with a hint of sweetness, and nearly springy to the touch; at its worst it is dense, flat and sticky. For that reason this recipe gives the batter as much space as the steaming does.
Where It Comes From
Idli is closely tied to Tamil Nadu and Karnataka and sits at the centre of what is called tiffin across the south, meaning the light, often savoury dishes eaten at breakfast or in the late afternoon. How the dish began is argued over by food historians. One line of thought places a steamed, fermented rice and lentil cake in South India more than a thousand years ago, while K.T. Achaya and others have raised the possibility of Indonesian influence, noting that early written mentions of something like idli turn up in the setting of trade between South India and Southeast Asia. Neither account has been settled, so this page leaves the deep past open instead of choosing between them. What can be said with confidence is that idli has been an ordinary part of home cooking and temple food in the south for many centuries, however the method first arrived.
How to Make It
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Prep
Soak the rice and dal apart
Wash the rice and leave it covered in water for four to six hours. In a second bowl, wash the urad dal along with the fenugreek and soak for the same length of time. Keeping the two apart is deliberate: dal wants a long grind to trap air, whereas rice should stay a little rougher.
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Prep
Whip the dal until pale and airy
Strain the soaking water from the dal and fenugreek, then put them into the grinder with a splash of cold water, just enough for the stones or blades to keep moving, and scrape the sides down every so often. The paste should be silky, pale and full of air, about double the volume of the dry dal. Expect to wait a quarter of an hour or more in a wet grinder, a little less in a strong blender; it feels excessive, but the aeration is the reason the idli will be light.
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Prep
Grind the rice to a coarser paste
Strain the rice and grind it separately, stopping while it still feels faintly gritty between the fingers. A bit of grain in the rice paste is acceptable, and welcome, since smoothness matters only for the dal.
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Prep
Mix by hand and let it ferment
Use your hand, not a machine, to blend the rice and dal batters, because machines can knock the air out. Do this in a big container, since the mixture can double in size or more while fermenting. Loosely cover it and keep it in a warm place at roughly 25 to 30°C (77 to 86°F) for eight to twelve hours, or overnight. When the kitchen is chilly, an oven with just its light on, or an Instant Pot set to the yogurt function, will hold a consistent warmth.
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Prep
Judge the fermentation
When fermentation has gone well the batter will have lifted, with a slightly domed top full of bubbles, and it will smell tangy and yeasty in a mild, agreeable way rather than harsh. Add the salt now and fold it in with a gentle hand, avoiding vigorous beating that would let the air out.
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Cook
Steam the idli
Brush a little oil in the moulds and ladle in batter until each hollow is three-quarters full. Set them into the steamer, or a deep pot with a rack, once the water below is boiling hard, and cook ten to twelve minutes. A toothpick comes out clean when they are done, and the surface bounces back when touched lightly.
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Serve
Wait a moment, then unmould
Leave the idli in the moulds for 2 to 3 minutes after steaming and loosen them with a wet spoon. They firm up a little as they cool and come out far more cleanly once they have. Serve hot with coconut chutney and sambar.
Swaps That Work
Three parts rice to one part urad dal is the classic ratio and rarely lets you down, and some households push the rice to four parts when they want a sturdier idli. Idli rava, which is parboiled rice broken into grit, replaces whole rice and is easier for beginners because it has been prepared for you. Methi seeds are optional, yet they help flavour and fermentation, so use them if you have them.
Turning the Heat Up or Down
There is no spice in an idli. Its appeal is soft texture and a faint tang, and the heat belongs to the chutney and sambar served alongside, both of which you can adjust freely without altering the idli.
Where Cooks Go Wrong
A batter that fails to rise is the usual complaint, and it traces back to a kitchen that is too cool, a dal that was not ground airy enough, or salt added before fermenting, because salt can slow the process, which is why it goes in afterward here. Idli that come out dense and flat even though the batter rose often point to a dal grind that was too coarse or to a batter that was stirred hard after it had risen, driving the air out. When idli cling to the moulds, the cause is generally too little grease or unmoulding them before they have had time to rest.
Keeping and Warming Up Leftovers
To keep: Batter stays usable in the fridge for four to five days, though fermentation does not stop in the cold, so the batter slowly grows more sour and thinner and tastes different on day four than on day one. Idli you have already steamed keep for two to three days in a closed box in the refrigerator.
To warm up: Put cooked idli back into the steamer for three to four minutes and they soften again; a quick turn in the microwave under a damp paper towel works too and prevents drying. Idli that have become hard and dry are difficult to rescue without extra water.
Safe Handling
Properly fermented batter is safe and should not be confused with spoiled batter. The difference shows in the smell and the look: a pleasantly sour, mildly yeasty aroma with even bubbling means fermentation, whereas a rotten or alcoholic smell, discolouration or mould means the batter has gone off and should be thrown away. Keep the batter loosely covered, not sealed airtight, since a tight lid can trap excess gas, and keep it clear of anything that might contaminate it. Once it has fermented as far as you want, move it to the refrigerator to slow it down.
Where to Read More
- K.T. Achaya, "Indian Food: A Historical Companion" (Oxford University Press) — on the debated early history and possible Southeast Asian influence on fermented rice-and-lentil cakes.