Wash the chana dal, urad dal, and toor dal all at once, and let them soak in water for 2 hours.
Add red chillis to the water.
Wash the moong dal by itself and soak it in water for 2 hours.
After 2 hours, drain the water and add salt, asafoetida, and turmeric powder to the soaked chana dal, urad dal, and toor dal and chillis mixture.
Grind this mixture into a semi-smooth consistency. If needed, sprinkle some water while grinding.
Transfer this into a bowl. Now drain the water from the moong dal and add it to the batter. Add the curry leaves and the cilantro. Mix it well.
Heat the oil in a kadai. Drop a small piece of vada batter into the oil. If the oil is hot, the batter will rise immediately and sizzle.
Wet your palms and shake off the excess water. Take a small gooseberry-sized vada batter, flatten it into small patties, and slowly drop it in oil.
Fry for 30 to 45 seconds and slowly flip them. Fry until the vada turns golden brown. By this time, the sizzling sound will reduce as well. Drain the fried vada on plain paper napkins.
Depending upon your kadai size, you can fry 3 to 4 in one batch. Similarly, flatten and fry the vada with the remaining batter.
Serve these vadas fresh and hot with the chutney of your choice.