Heat oil in a frying pan.2)Add mustard seeds. 3)When they pop, add the two dhals, asafoetida and cashew nuts. 4)Fry them until golden brown. 5)Add rava, salt and cooking soda and roast it until you get the aroma of the roasted rava.6)Allow Rava to cool, add yogurt to this mixture. 7)Blend well.8)Pour it in the idly vessel and steam it. 9)Your Rava idly (rice balls) is ready to serve with chutney or sambhar, Serve hot.