Slice the potatoes thinly in rounds. Keep them in water till needed.
Mix well the besan, rice flour, ajwain, red chilli powder, hing and soda with water. Remember to use little water as more can be added if needed. The batter has to be thick.
Check the seasoning and add more if required.
Heat oil for frying in a kadhai/wok.
Now transfer the potato slices, few at a time to a clean kitchen napkin so that the slices are not damp.
Dip each potato slice in the batter and place it gently in hot oil.