My mom adds Rice flour
to the pakora batter to make them crispy. Adding corn flour
works equally well. Just replace part of the Besan/Chickpea flour with little of the said flour. For less retention of oil, the frying oil needs to be at the correct temperature - between 325°F and 400°F
. Adding few teaspoons of the hot oil to the batter before frying also helps. Remember to fry only in small batches to avoid bringing down the temperature of the oil which will lead to soggy pakoras.
Here are some recipes for Pakoras