Mix semolina and curd together, add salt as per taste.
Mix this batter thoroughly and keep it aside for at least 45 minutes.
Take a small pan on medium heat and add oil into it.
Once oil is hot, add mustard seeds.
Seeds will start spluttering then add curry leaves, chana dal and urad dal.
Add cashews at the end and let it roast slightly.
Once tempering is ready remove it from heat and keep aside. Add it into the batter after 45 minutes and mix everything together.
At this point, batter is very thick hence need to add water to get perfect consistency.
Carefully add water until it is semi thick and can be poured into the moulds for steaming. Batter should not be watery but thin enough to pour and steam into the moulds.
Add soda into this batter and whisk it gently. Always add soda, at the very end - just before transferring batter into moulds for steaming.
Grease the Idli moulds and pour this batter into it. Steam these Idli's for 10-15 minutes over hot boiling water.
To check whether Idli's are ready or not - touch top of Idli with wet fingertips if batter is not sticking to the fingertip then its ready. Another way to check by inserting toothpick and if it comes out clean then Idli is ready.
Cool down the mould and Idli's can be easily removed from it. Rawa Idli's are ready to serve.