Wash the dals together and soak them along with the red chillies for 30 minutes. Drain well and let them rest in a colander for 15-20 minutes.
Grind the dals, red chillies, asafoetida, salt to a coarse mixture. Do not add any water to grind.
Boil water in a idli pot or steamer. Spread the dal mixture on greased idli plate or steamer plate and steam for 5-6 minutes. Set aside to cool.
Once cool, remove from plates and crumble them with hands. Set aside.
Heat oil in a pan and add mustard seeds. Once it splutters, add urad dal, red chillies, curry leaves and asafoetida.
Once the dal turns golden, add the beans, turmeric powder, salt and combine well. Cover and cook for 4-5 minutes or until beans is cooked.
Now add the crumbled dal mixture and combine well with the beans. Fry for 3-4 minutes and remove from heat.