Wash and soak all three dals in a bowl for 2 hours, or in hot water for 1&1/2 hours.
Clean and wash beans. Finely chop them. Add to a bowl with water and pinch of turmeric and keep in a pressure cooker, with little water in the base. Steam cook till 2 whistles
After soaking the dals, remove all the water and grind them dry, coarsely with hing, turmeric, chillies and salt.
Remove in a bowl that fits in a pressure cooker or in a cooker container. Steam cook until 1 whistle.
Now lets prepare the Usili. Add oil a non stick pan and add mustard seeds, let splutter, add curry leaves and fry.
Now add the steamed dal by breaking it with the spatula. Mix well and let cook in the oil for 3-5 minutes.
Add the vegetable and mix well. Cover and let the flavours mix for sometime. This will take another 3-5 minutes.
Once the dal looks tender and doesn't stick with each other, it means the dish is ready.
Serve hot with steamed rice and vatha kuzhambu.
