Bring water to a boil in a sauce pan. When it starts to boil, take it off the heat and add in salt and oil.
Add in rice flour and mix well. It will get thick. Now cover it and let it cool down.
Now take urad dal in a bowl and cover it with water. Soak it for 2 hours.Now drain them and set aside.
Take green chillies in a blender and crush it. Add in urad dal and pulse it few times till it is coarse mix.
Now take it in a bowl and add some salt to taste and mix well.
Take the urad dal mix and place it in a idli steamer. Steam it for 10 to 12 mins.
Remove it and cool slightly, then crumble it using your hands.
Now heat oil in a kadai, add in mustard seeds, urad dal and curry leaves.
Add in the urad dal mix and saute well. Use your spatula to crumble it so it gets finer.
Add in coconut and mix well. Remove the stuffing to a bowl and let it cool.
Now take a small portion of ball and flatten it slightly. fill it with urad dal mix and cover it.Seal the edges.
Place it in a steamer and steam for 7 to 8 mins.
Remove it and let it cool for 5 mins. Remove it carefully from the steamer and Serve.