The basic dosa is made by soaking urad dal / skinned black lentils and rice. The soaked lentils and rice are then finely ground and fermented overnight. Warm temperature is very important for the batter to ferment well. Once the batter is ready, spread a thin layer over the griddle in circular manner with heated oil in the edges. A potato masala is traditionally used as a filling, and is often served with spicy sambhar and coconut chutney.