Dry roast oats for few minutes or until oats is crispy, cool and grind into powder.
Heat oil in a pan, splutter mustard seeds, add chana dal, urad dal and fry until golden brown.
Now add asafoetida, ginger paste, curry leaves, green chilly and saute for few minutes.
Add grated carrot and saute for another minute.Now add semolina / rava and fry for 2-3 minutes. Off the flame and add oats powder. Mix everything well.
Once the mixture is cool, add curd and 1/2 water and mix well. Keep it aside for 15 minutes.
Meanwhile grease the idli plates. Boil water in idli cooker.
Add more water if needed to make idli batter consistency. Add coriander leaf and soda just before pouring batter into the idli plates. Keep one cashew in each mould , before pouring batter.
Steam for 15 minutes on medium low flame.
Serve hot with sambar or chutney.