Overview
The batter behind dosa is almost the same as the one used for idli, yet the work after fermentation calls for another kind of skill. One ladle is drawn out across a hot griddle into a wide, thin disc, and the disc has to crisp at its rim while the middle finishes cooking and turns gold. Few South Indian dishes lean so heavily on handling. Excellent batter still gives a poor dosa when the pan is the wrong heat or the hand hesitates while spreading. A successful dosa is thin and brittle with a faint sourness from fermentation. It is eaten plain beside chutney and sambar, or rolled around a filling, the spiced potato of masala dosa being the best known.
Where the Dish Comes From
Where dosa first appeared cannot be settled, any more than for idli. Both belong to the South Indian habit of fermenting batters, and the written evidence for each is thin and contested. What can be documented is the central place of dosa in the food culture of Tamil Nadu and Karnataka, and the distinct regional styles that developed there. The very large, paper-thin dosa associated with restaurants around Chennai differs from the thicker and more textured kind eaten in parts of rural Tamil Nadu and Karnataka. Udupi, on the coast of Karnataka, is particularly credited with spreading the masala dosa format, a dosa filled with spiced potato, which later travelled across India and abroad through Udupi-style restaurants.
Step-by-Step Method
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Prep
Adjust the batter consistency
A runnier mixture than idli batter is required, about as loose as thick pancake batter, which flows off a ladle yet still coats it. Stirring in water by the spoonful and checking after each addition reaches that point. How much is needed varies with the length of fermentation and the thickness the batter had initially.
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Prep
Heat and season the griddle
Medium-high heat is applied to a flat griddle or broad pan until a sprinkled drop of water hisses and disappears within a second or two. An onion half dipped in oil, or an oily cloth, is then rubbed over the surface. That coating primes the pan so the first dosa releases cleanly, and the first one is usually the hardest to lift.
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Cook
Pour and spread in a single motion
The heat is lowered a little, to medium. A ladleful of batter goes onto the centre of the griddle and is spread at once outward, in one quick and continuous spiral made with the base of the ladle, from the middle to the edge, until it forms a thin, even circle. Pausing partway through the spiral produces uneven thickness, so the movement should be committed to once it begins.
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Cook
Add oil and cook until crisp
Oil or ghee, only a teaspoon or so, is trickled along the rim and over the face of the crepe. After that the dosa is left alone for 1 1/2 to 2 minutes. The signs of readiness are edges that curl away from the pan with a brown colour, and a centre that looks matte and firm instead of glossy. Turning it too soon spoils the crust, and a thin, crisp dosa frequently needs no turning whatsoever.
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Cook
Fold or fill, then lift off
When the underside is deep golden and crisp, the dosa is folded in half or in thirds with a flat spatula and slid onto the plate. For masala dosa, a potato filling is spread along the centre before folding. Between dosas, the heat is lowered a little if the pan runs too hot, and raised slightly if the batter is not spreading or crisping fast enough.
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Serve
Serve the moment it is ready
A dosa is at its best straight from the griddle, while it is still audibly crisp, and it softens within a few minutes. It is served with coconut chutney and sambar.
Ingredient Swaps
Age changes the outcome. A one-day batter yields a softer, milder dosa, while a batter two or three days old gives a crisper and more sour one, and either result is acceptable. Cooks who want extra crispness sometimes grind a spoon of cooked rice or add a pinch of sugar to the batter, a habit that is common in some kitchens and absent in others.
Turning the Heat Up or Down
The crepe itself is unseasoned beyond salt. Any warmth reaches the plate through the chutneys, the sambar or a spiced filling like the masala dosa potato, and each of those is tuned on its own terms, so nothing needs correcting in the batter.
Frequent Errors
Heat in the pan outweighs every other variable. A cool pan stops the batter from thinning out and crisping, and it catches and rips. A scorching one sets the batter on contact, before the ladle can move, leaving a thick and lumpy disc. The second most frequent fault is hesitant spreading, because stopping partway through the spiral leaves thick patches. The third is failing to season the pan properly before the first few dosas, which causes early sticking. That usually resolves itself after two or three dosas, as the surface builds a light coating.
Keeping and Warming Leftovers
To keep: Dosa batter keeps in the refrigerator for 4 to 5 days and continues to ferment slowly, growing more sour over that time. It thickens on standing, so it is thinned with water before each use. Cooked dosas neither store nor reheat well, because their appeal lies almost wholly in being fresh and crisp.
To warm: Leftover dosa regains some snap after about a minute per side in an ungreased pan at medium heat, though it never equals one cooked a moment earlier. Cooking to order suits this dish better than preparing it ahead.
Safe Handling
As with idli batter, well-fermented dosa batter has a pleasant, mild sourness. Batter that smells sharp, alcoholic or rotten, or that shows discolouration or mould, is discarded and not cooked. Once fermentation has reached the desired point, the batter is kept refrigerated between uses, and only the portion needed is brought briefly to room temperature, which makes it easier to spread.