The ideal consistency for idli batter is similar to that of semolina porridge or a thick milkshake, allowing it to hold its shape briefly before slowly spreading. It should be easily pourable but not too runny.
Achieving the right consistency is crucial for soft and fluffy idlis. Here's a breakdown:
Ingredients Ratio: The typical ratio is 2 parts idli rice to 1 part urad dal (split black lentils). Soaking these separately for at least 4-6 hours is essential.
Grinding: Grind the urad dal first with enough water to form a light and airy batter. Then, grind the rice separately to a slightly coarse consistency, like semolina.
Mixing: Combine the urad dal and rice batters thoroughly. Add salt to taste. The batter should not be too thick or too thin. If it's too thick, add a little water, one tablespoon at a time, until you reach the desired consistency. If it's too thin, you can add a tablespoon or two of rice flour, but this is generally not recommended as it can affect the texture.
Fermentation: Ferment the batter for 8-12 hours, or until it has doubled in volume. The fermentation process is what gives idlis their light and airy texture. The batter will become slightly more liquid after fermentation.
Final Check: After fermentation, gently stir the batter. It should still have a thick, pourable consistency. If it has become too thick during fermentation, add a little water to adjust.
Use a wet grinder for the best results. A wet grinder produces a smoother, more consistent batter than a blender or food processor, leading to softer idlis. If using a blender, grind in small batches and avoid overheating the batter.