- Dry roast the rava on medium flame for 2-3 minutes. further, cool them completely before preparing idli. now transfer the dry roasted rava to a large mixing bowl. also add ragi flour to it. furthermore add salt and curd. add water as required depending on curd thickness. give a good mix and allow to soak for 30 minutes. after 30 minutes, mix well and add water if required. get to idli batter consistency. just before steaming add a pinch of baking soda and mix well till it turns frothy. brush the plates with oil and pour the batter immediately into the idli plate. also as other idlis you have to steam it for 8-10 mins on medium flame. furthermore, allow it to rest for 5 mins then unmould. finally, serve hot with coconut chutney and sambar.