Overview
On paper, idli is about as modest as a dish can be: two ingredients, ground, soured and steamed. In a kitchen it behaves differently, because the entire character of the dish is settled by an overnight fermentation that nobody can watch or adjust once it has begun. That fact organises this entry. Texture follows from the batter, and the batter follows from four earlier decisions, namely how long the grains soak, how finely each is ground, how warm the batter is kept, and when the salt goes in. Get those right and the steamer simply finishes the job, producing cakes that are soft, mildly acidic and almost spongy. Get them wrong and the same steamer produces dense, flat, sticky discs. For this reason the steaming instructions come last and are brief, whereas the earlier steps are described in detail.
Where the Dish Comes From
The roots of idli lie in Tamil Nadu and Karnataka, and the dish forms a pillar of what South Indians call tiffin, a category of light morning and afternoon foods that are frequently savoury. Scholars disagree about where it came from. One view traces a steamed, fermented rice-and-lentil cake to South India more than a millennium ago. A competing view, associated with K.T. Achaya, suggests Indonesian influence, because the earliest texts that mention something close to idli arise from the commercial links between South India and Southeast Asia. Neither case is proven, so the honest summary is that the dish's earliest history is open. What can be said with confidence is that idli has held a regular place in southern household cooking and temple offerings for many centuries.
Step-by-Step Method
-
Prep
Keep the rice and the dal in separate soaks
Cover the rinsed rice with water for between 4 and 6 hours. Treat the dal the same way in its own bowl, adding the fenugreek seeds to it. Separation is deliberate. Dal has to be whipped for a good while to hold air, and rice does best when ground less thoroughly, so the two cannot share a grinding cycle.
-
Prep
Grind the dal to a pale, fluffy mass
Strain the dal and fenugreek and start the grinder with the smallest splash of cold water that keeps the blades moving, stopping to push batter down from the walls. The correct end point is a smooth, light-coloured foam roughly double its dry volume. A wet grinder may need 15 to 20 minutes and a strong blender fewer. The wait feels long, but the air trapped here is what lifts the finished cake.
-
Prep
Leave the rice with a little grit
After straining, grind the rice by itself into a thick paste that still feels faintly sandy between the fingers. Some coarseness helps, in contrast to the dal, which should be as smooth and aerated as possible.
-
Prep
Mix by hand and give the batter time to rise
Use your hand and not a blender to combine the two pastes, since machines drive out the bubbles. Choose a big vessel, because the mixture can double or more as it ferments. A loose cover and a warm location of about 25 to 30°C (77 to 86°F) for 8 to 12 hours, or overnight, are what it needs. In chilly weather, a switched-off oven with the bulb lit, or a pressure appliance on its yogurt mode, holds the temperature steady.
-
Prep
Look and smell before adding salt
A batter that has fermented well stands noticeably taller, wears a domed top full of small bubbles, and gives off a gentle, yeasty sourness that is pleasant and not sharp. Once it passes that test, fold in the salt with slow strokes to avoid knocking out the structure.
-
Cook
Fill the moulds and steam
Brush the moulds with a little oil and spoon batter into each hollow until it is about three-quarters full. Place the stand over water that is boiling hard and steam for 10 to 12 minutes. A cake is cooked when a toothpick leaves it clean and a finger press springs back.
-
Serve
Wait briefly before lifting them out
Allow the idli to rest 2 to 3 minutes, then ease each one out with a wet spoon. They firm up as they cool, and a firmer idli leaves the mould neatly. Serve them warm with coconut chutney and sambar.
Ingredient Swaps
Three parts rice to one part urad dal is the standard proportion and works dependably. A number of households push the rice to four parts for a slightly heavier cake. Idli rava, which is a coarse parboiled rice semolina, can take the place of whole rice and suits first-time fermenters well, as it arrives already processed. The fenugreek can be dropped, though it benefits flavour and fermentation and is worth adding when to hand.
Turning the Heat Up or Down
Idli is not seasoned itself. Its charm is texture and a faint tang. Any spiciness comes from the accompaniments, so chutney and sambar can be made as mild or as hot as desired with no effect on the cakes.
Frequent Errors
A batter that refuses to rise nearly always has one of three causes. The kitchen may be cold, the dal may have been ground without enough air, or the salt may have gone in before fermentation, which can hold back the microbes and is why it waits until afterward. Cakes that stay heavy and flat even after a good rise usually point to a gritty dal grind, or to rough stirring after fermentation that deflated the batter. Cakes that cling to their moulds were probably under-greased or taken out before they rested.
Keeping and Warming Leftovers
To keep: Fermented batter will keep for 4 to 5 days in the refrigerator, but it goes on fermenting slowly there, so a day-four batter is sourer and looser than it was on day one. Steamed idli can be refrigerated in a closed container for 2 to 3 days.
To warm: Put cooked idli back in the steamer for 3 to 4 minutes to soften them, or cover them with a moist paper towel and use the microwave for a short time. Idli that have hardened and dried out do not recover well unless moisture is added.
Safe Handling
Batter that has fermented properly is a safe food and should not be confused with spoiled batter. Smell and look tell them apart: a clean sourness with a yeasty note and evenly spread bubbles means active fermentation, while a rotten or boozy odour, a change of colour or any mould means the batter has gone off and must be thrown away. During fermentation the lid should rest loosely, not seal tightly, as a sealed lid can hold in too much gas. Keep the container clean and put it in the refrigerator when fermentation has gone as far as is wanted.
References
- 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.