How to Make It
Rinse the 2 kinds of dhal separately in several changes of water, then soak for 4 hours. Drain before using. In a food processor, combine the dhals with the water and pulse until finely ground but not pureed. Transfer the dhals to a medium bowl and add the onion, cilantro, ginger, serrano chile, cumin, cayenne, asafetida and 1 1/4 teaspoons of salt.
In a wok, heat 2 inches of oil to 325°. Scoop scant tablespoons of the vada batter onto a wax paperlined plate and flatten slightly. Slide 5 or 6 patties at a time into the hot oil and cook, turning once, until deep golden brown, about 5 minutes. Using a slotted spoon, transfer the fritters to paper towels to drain. Sprinkle with salt and serve at once.