Dry roast the gram flour/ besan ,till nice aroma waft .Take measures not to darken the flour.
Wash and clean fish slices, let water drain completely , set aside.
Place fish in a bowl / container , add ginger garlic paste , salt , mustard oil , lemon juice, tandoori masala, ½ teaspoon ajwain and all other spices listed in ingredient list except Besan/ gram flour.
Rub in all masala to fish , such that its well coated with spices. Allow the marination to stand for minimum 30 minutes or upto 6-8 hrs .
Heat a tawa , drizzle 1 tablespoon of oil , add ajwain seeds , once it crackles arrange marinated fish pieces on tawa .
Allow fish to cook for 5-6 minutes on medium heat ,flip and cook on other side for another 2-3 minutes.
Sprinkle roasted gram flour / besan over the fish ,such that its coated well .Flip and again sprinkle some gram flour on other side of the fish.
Drizzle some oil on top , flip and cook on both sides ,till crisp.Sprinkle some chat masala on top of fried fish and serve.
Serve Amritsari Fish Tawa Fry , with lemon wedges ,onion rings and coriander mint chutney.