Take the Rava in a bowl, add finely chop the onions, chilies and coriander leaves, curry leaves along with cumin seeds, soda, and salt.
Add curds and mix well. Now depending on how thick the batter is, sprinkle some water and mix well.
Let this sit for 30 mins. The batter is quite thick at this stage and you might have to add a few tsp of water later.
After 30 mins, heat the Kadai with oil.
Mix the batter again and check if it requires some water. So add few tsp and mix again.
Take a small ball, wet your palm, flatten the ball into thin discs and gently slide into the hot oil.
Cook on a medium flame until the vadas are cooked on both sides.
Drain on a kitchen towel and serve hot.