Soak 1/2 cup toor dal with 2 tbsp chana dal and 2 dried red chillies, for 2-3 hours
Drain well and grind this to a coarse paste with 1/4 tsp of asafoetida powder, without adding extra water.
In a non-stick pan, heat 1 tbsp oil. Add the ground dal mixture and start crumbling the mixture using a wooden spatula. Roast on a low flame, until the crumbled dal paste is well cooked and starts to crisp up. This takes 12-15 minutes.
Meanwhile, steam the beans in the pressure cooker or stove top in a pan with very little water and a pinch of salt (or microwave). Once beans are cooked, but still green, remove from pan and drain any excess water. Reserve this water for any other dish.
Add the beans to the crisped up crumble. Add some salt if required.
In a tadka ladle, heat 1 tsp oil. Prepare the tadka using curry leaves, udad dal, mustard seeds. Once mustard seeds splutter, udad dal turns golden brown, transfer it over the usili.
Garnish with some fresh coconut scrapings.