Rinse the chana dal and toor dal together and soak them in water for about an hour.
While the dal is soaking, wash and clean the fresh beans. Finely chop the beans and steam the beans along with a little bit of salt, in a pressure cooker for two whistkles or until tender. Set them aside. If you don't want to use the pressure cooker, you can cook the beans by sautéing in the pan itself.
After an hour of soaking the dals, drain the dals and grind them along with dried red chilies, a pinch of asafoetida and salt into a coarse paste without adding too much water. The mixture should be coarse and not too watery.
Grease a steaming vessel or plate with a little oil. Spread the ground dal mixture evenly on the plate.
Steam the dal mixture for about 10 minutes until it's cooked through. You can insert a toothpick or a knife to check for doneness. The dal mixture should be firm.
Once the paruppu / dal mixture is cooked, allow it to cool. Then, crumble it using your fingers. Paruppu usili is ready.
In a separate pan, heat a little oil and add mustard seeds, and red chilli. Once they start spluttering, add fresh curry leaves and the steamed dal pieces along with turmeric powder. Sauté for a few minutes.
Add the cooked beans to the cooked paruppusili and mix them together. Taste and add salt if needed.
Once the dal pieces are crispy and coated with the beans, remove the beans paruppu usili from heat. Optionally, garnish with freshly chopped coriander leaves before serving.
Serve the beans paruppusili with rice and your choice of kuzhambu or rasam.