Peel and cut the potatoes into thin rounds either with a mandoline or a sharp knife. The slices are approximately 2mm thick. Wet them in cold water for ten minutes to make them dry off all the starch and then pat them.
Sieve the gram flour and rice flour in a large mixing bowl and remove all lumps. Add hing, garam masala, red chili powder, ajwain, turmeric, salt and chopped coriander leaves.
Add water gradually to the flour mixture and cause it to mix uniformly to make a thick batter. It must be thick enough not to drip off right away yet be thick enough so as to coat the back of a spoon. Allow the batter to rest for 10 minutes.
Add oil into a deep kadai or frying pan and heat it on medium-high heat. To test whether the oil is prepared, place a bit of batter on it, and, should it immediately rise to the surface, the oil is prepared.
Coat each slice of potatoes with batter making sure that there is no part that is not covered. Gently add the slices that are coated into a hot oil one at a time. Do not overcrowd the pan.
Fry the pakoras on medium heat, turning them every now and then, till it is puffed and golden brown on both sides. Blot and dry using a paper towel. Serve hot.