Start by making the filling. Heat oil in a kadai. Add all the tempering ingredients and sauté for a min.
Add in onions and green chilli and mix well. Cook for 2 mins.
Add in chilli, coriander, salt and turmeric powder and mix well. Add in all the vegetables and sauté for 5 mins.
Pour a splash of water and mix well. Cover the pan and let it cook for 10 mins. Filling is done.
Now take your idli plates and grease it. Spoon a tbsp of batter in the bottom and spoon a tbsp of this vegetable mixture on top. Now spoon a tbsp of batter again on top. Make sure that everything is totally covered.
Put this in the idli stand and let it steam for 15 mins.