- Pressure cook toor dal with 1 cup of water for 4 whistles in medium flame. Mash it well once done. Soak tamarind in hot water and extract tamarind juice. In luke-warm water (¼ cup), grind coconut and extract milk. Keep aside. Boil tamarind extract, with added one more cup of water, along with finely chopped tomato and slit green chilli. Let it boil for 5 mins. Add rasam powder, turmeric, salt and sugar. Bring to boil. Add mashed dal and adjust water if needed. Bring to boil again and once its frothy, add coconut milk and switch off the flame immediately. In a pan, heat ghee, temper with mustard, red chilli, asafoetida, cumin seeds and lastly coriander leaves. Add this tadka to rasam and finally garnish with coriander leaves. Make idli and place it in serving bowl. Add the hot rasam in idli. Garnish with finely chopped onion and coriander. Serve hot.