Toast the coriander and cumin seeds in a small frypan on medium heat. When the seeds turn darker and become fragrant, take off the heat, cool and grind to a coarse mixture in a spice grinder. Take care not to grind the spices very fine.
Grind the white rice in a spice grinder to a fine powder.
To the mashed potatoes, add all the powdered spices - coriander, cumin, half the chaat masala (½ tsp), pomegranate, red chilli, ginger, and turmeric. Also add salt, rice flour and cornflour. Mix well using your hands if necessary.
Grease the palms of your hands with a little oil and shape the potato mixture into tennis-sized balls or smaller if you want to. Flatten them into thick discs.
Heat the oil in a frypan to medium-hot and slide in the prepared discs. Let them fry in the hot oil for 3-4 minutes or until golden-brown on the underside. Flip the discs and repeat. You can do this in batches to avoid overcrowding using more oil if necessary. Take out the aloo tikki in a platter and lightly sprinkle the remaining chaat masala on top.
Serve with the chutney of your choice.
Notes
If you need detailed notes on how to boil potatoes, see the body of the post.
You can use readymade coriander and cumin powders if you don't want to toast and grind your own, but these do not add as much flavor to the aloo tikkis.
If you don't want to use up all the tikkis, they can be easily frozen in ziploc bags. Thaw the bag in a bowl of water and fry as usual when you want to.
You can add a few extras to the tikkis like steamed sweet peas, paneer or green chillies and cilantro leaves to make them more interesting. If adding green chillies, skip the red chilli powder or use less of it.
Try drizzling a little yogurt sweetened with sugar on the tikkis for another variation. Yogurt goes very well with them and along with the tamarind and coriander chutneys, transforms the plain tikkis into aloo tikki chaat!