To make a batter for vada, first clean, wash and then soak dal in water for 5 - 6 hours or overnight.
The next day, transfer the soaked dal to a colander, drain all the water. Let dal sit in the colander for 5 minutes so that all the excess water drains out.
Transfer dal to the grinder with chopped green chilies and ginger. Grind dal in the mixer without using water, stop mixer in between, stir dal with a spatula and then grind. Keep doing this at regular intervals. If still, dal is not turning into a smooth paste, add 1 – 2 tablespoon of water, then grind. The idea is to use minimum water to grind the dal. Grinding dal usually takes 10 – 15 minutes depending on the mixer.
Once dal is turned into a smooth paste, transfer to a large bowl. Add salt, asafoetida, turmeric, and whisk batter briskly for 8 - 10 minutes or till it is light and fluffy.
To deep fry vadas, heat oil in a deep frying pan over medium heat.
Using two spoons, shape the batter into a round and gently slide into the hot oil for frying.
Don’t be in a hurry to turn the vada. Let them turn golden from one side. When the vada turns pale golden from the base and sides, you can turn them. Fry the vadas till they become golden and crisp.
Transfer fried vadas in a plate lined with paper towels. Once all the vadas are fried, turn off the heat.