Make sure the oil is hot before you add the vadas into the oil.
I like to test it by adding little drops of chickpea flour batter in the oil, if it comes up and starts to float, the oil it ready. If the batter sinks, and takes time to come up, then let the oil heat up for another 5 minutes, and test again.
Add the prepared potato filling balls to the prepared besan batter.
Use a fork or spoon, to coat the batter on the potato filling from all sides.
Drop the potato balls carefully in the hot oil.
Depending on the size of the kadai, add more or less vadas at the same time for frying. You don't want your kadai to be very crowded. I use about 8inch kadai, and I fry 3 vadas at a time.
Once the batata vada, starts to lightly turn golden and crisp on one side, using a strainer ladle turn them to cook from all sides.
When the batata vadas look crispy and golden from the outside, it's time to take them out.
Layer a plate with a paper towel. Place the fried vadas in this plate to drain off the excess oil.
Similarly fry all the vadas.