Can you explain the process of making dosa batter from scratch, including the soaking and fermentation steps?

Making dosa batter from scratch involves soaking rice and urad dal (black gram lentils) separately for several hours or overnight. The soaked ingredients are then ground into a smooth paste, mixed together, and left to ferment for at least 8-12 hours. Fermentation is key as it creates a light and airy texture in the dosa batter, resulting in crispy and flavorful dosas when cooked. The fermented batter is seasoned with salt and can be used to make dosas immediately or stored in the refrigerator for later use.