Heat ghee in a pan, add mustard seeds and let it splutter. Add cumin seeds, urid dal, asafoetida and turmeric powder. Sauté for 30 seconds.
Add grated carrots, green chillies, ginger and curry leaves, sauté for two minutes. Lower the heat, add a cup of rava and roast until its aromatic. Remove from heat and let it cool completely.
Add yogurt to the rava mixture. Mix well, adding water adequately until you get a smooth batter. Keep it aside for 10-15 minutes.
Add baking soda to the mixture and combine everything well.
Grease the idli moulds with oil. Pour the batter into them and steam for 10 minutes on high heat. Serve with your favourite chutney or sambhar.