Idli and dosa are two popular South Indian dishes that are made using fermented batters. The batters are typically made from a combination of rice and lentils (urad dal), and water.
The idli batter is made by soaking rice and urad dal separately for a few hours, grinding them into a fine paste, mixing them together with water and allowing the mixture to ferment overnight. This batter is then used to make soft, fluffy and spongy idlis which are typically eaten for breakfast or as a snack.
The dosa batter, on the other hand, is made using the same ingredients as the idli batter but with a different ratio of rice and urad dal. The batter is allowed to ferment for a longer period of time to develop a tangy flavor and sour taste. This batter is then used to make thin, crispy crepes called dosas, which are usually eaten for breakfast or as a main course with a variety of fillings.
Both idli and dosa batters require proper fermentation to achieve the desired texture and flavor, and the process may vary slightly depending on the region and the family recipe.