Introduction
A dosa begins with nearly the same fermented batter as an idli, yet what happens after fermentation is a different craft altogether. The cook ladles batter onto a hot griddle, spreads it outward into a wide, thin, even circle, and must get the rim crisp while the whole crepe sets in the short time the centre needs to colour. Of all the recipes in the collection, this is one of the most dependent on technique, because a perfect batter can still produce a poor dosa if the pan is at the wrong heat or the hand hesitates during spreading. When it works, the dosa is thin, crackling and faintly sour from the fermentation, and it can be eaten plain with chutney and sambar or wrapped around a filling such as the spiced potato of masala dosa.
Origin & Cultural Context
The beginnings of dosa are as uncertain as those of idli, since both come from the same South Indian tradition of fermented batters and the historical record for each is patchy and argued over. What is well established is how central dosa has long been to the food of Tamil Nadu and Karnataka, where several regional styles developed their own identities: the huge, paper-thin dosa associated with the restaurants of the Chennai area is quite unlike the thicker, slightly more textured kind eaten in parts of rural Tamil Nadu and Karnataka, while Udupi, on the coast of Karnataka, is particularly credited with popularising the masala dosa, a dosa filled with spiced potato, which later travelled across India and abroad through Udupi-style restaurants.
Method
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Prep
Loosen the batter
Dosa batter needs to be clearly thinner than the batter for idli, about like a thick pancake batter that pours but still has some body. Stir in water a spoonful at a time until it gets there, and expect the amount to vary with how long the batter has fermented and how thick it was to begin with.
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Prep
Heat and season the griddle
Set a flat griddle or large pan over medium-high heat until a flick of water sizzles and disappears within a second or two. Rub the surface lightly with half an onion dipped in oil, or wipe it with an oiled cloth, which seasons the pan and helps the first dosa lift off cleanly, usually the hardest of the batch.
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Cook
Pour and spread in a single sweep
Turn the heat down slightly to medium. Pour a ladleful of batter onto the middle of the griddle and, without pausing, spread it outward in one steady spiral with the base of the ladle, working from the centre to the rim until the circle is thin and even. A hesitation halfway through leaves uneven thickness, so once you begin, follow the motion through.
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Cook
Drizzle oil and wait for crispness
Trickle a little oil or ghee around the edge and across the surface. Leave the dosa untouched for 1 1/2 to 2 minutes, until the rim visibly lifts and browns and the top looks dry and set instead of wet. Do not flip it early, since a thin, crisp dosa often needs no flipping at all.
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Cook
Fold or fill, then lift off
When the underside is deep golden and crisp, use a flat spatula to fold the dosa in half or in thirds and slide it onto a plate, or, for masala dosa, spread potato filling down the middle before folding. Lower the heat a little between dosas if the pan runs too hot, and raise it if the batter will not spread or crisp quickly enough.
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Serve
Eat straight from the pan
A dosa is best served the moment it leaves the griddle, while it still crackles when touched, because it softens within minutes. Bring it to the table with coconut chutney and sambar.
Substitutions
Batter that has fermented for only a day will give a softer, less tangy dosa than batter that is 2 to 3 days old, and both are legitimate, although the longer-fermented batter usually makes a crisper and more sour result. Blending in a small amount of cooked rice or a pinch of sugar is a common trick for extra crispness, though it is not traditional everywhere.
Adjusting the Spice Level
A plain dosa has no spice of its own, and the heat and flavour come from the chutneys, the sambar or a spiced filling like the one in masala dosa, each of which can be adjusted separately to suit your taste.
Common Mistakes
Pan temperature is the single largest factor in success. If it is too cool, the batter will not spread thinly or crisp and will stick and tear, and if it is too hot, the batter sets the instant it lands, before you can spread it, and gives a thick, uneven dosa. Hesitant spreading ranks second, because stopping midway through the spiral leaves thick patches. A third problem is failing to season the pan properly during the first few dosas, which leads to early sticking, though this usually fixes itself after two or three as the surface builds up a light coating.
Storage & Reheating
Storage: Dosa batter keeps in the refrigerator for up to 4 to 5 days while fermenting slowly and growing more sour, and it thickens as it stands, so thin it with water before each use. Cooked dosas neither store nor reheat well, since their charm lies almost entirely in being fresh and crisp.
Reheating: A cooked dosa can be warmed in a dry pan over medium heat for about a minute per side to regain part of its crispness, but it will not match a fresh one, and dosa is better cooked to order than made in advance.
Food Safety
As with idli batter, properly fermented dosa batter has a pleasant, mild sourness. Throw away any batter that smells sharply off, alcoholic or rotten, or that shows discolouration or mould, and do not cook with it. Once the batter has fermented as far as you want, keep it chilled between uses, and bring only the portion you are about to cook to room temperature for a short time so it spreads more easily.