Whisk the yogurt and add about 2 cups of water and mix.
Heat oil and add cashew nuts and roast on low heat till it turn golden in colour ,now remove the roasted cashew from the pan and keep aside .
In the same pan now add white lentil and mustard seeds,when the mustard start to crackle then add the curry leaves and stir
Add this tempering and the roasted cashews in the yogurt mix .
Now add the semolina , ginger and salt in the yogurt and mix well.
Cover the bowl and let it rest for an hour (you can use it after 15 minutes but soaking for 1-3 hours gives best result, )
Add water in the batter to adjust the consistency (the batter should be like the normal rice idli batter )
Now add 1.5 glass of water in your idli steamer and let it come to a rolling boil.
Grease the idli mould with oil and keep it ready.
When the water in the steamer start to boil then add Eno fruit salt in the batter and mix well.(If you are making idli in batches then don't add Eno in the whole batter ,just add Eno in each batch batter separately)
Fill the idli mould with batter and arrange in the steamer.
Steam for 10 minutes on high heat OR till a tooth pick came out clean from the idli. switch off the flame and let it rest for 2-3 minutes .
Now open the steamer and scoop out the idlis with a wet spoon.
Serve soft rava idlis with hot with coconut chutney and tomato chutney.