In a bowl, take all the ingredients and slowly mix it with hot milk using a spoon. The consistency should be of pouring state as the regular Idli batter.
Allow it to rest for 10 - 15 mins. Check the consistency to make sure the rava has not absorbed all the milk, if required add little more hot milk.
Then, pour the batter into greased idli moulds and steam as you would do with regular idlis.