Heat a spoon of oil in a skillet and fry the fish for about 10-15 minutes, adding a little of all the masalas (add garam masala in the end) till the fish becomes slightly dry and golden brown. Take it out of the skillet and place in a large shallow dish. Take some more oil, heat it and then fry the onions till golden brown.
Add the ginger, garlic and fry for a couple for minutes.
Add the rest of the powders(add garam masala in the end) and fry some more. Then add the tomato paste, cilantro, green chillies and fry till you can see the oil separate.
Turn off the heat. Now, add this onion masala along with the mashed potatoes to the fish in the shallow pan and knead well. Do not add too much of the potato. Add just enough to bind the fish together or you will not get the taste of the fish.
Shape this fish mixture into chops.
Then dip in the egg mixture, then in bread crumbs placed in a shallow bowl. Dip in egg again, then again in the bread crumbs and deep fry till dark brown.
Drain on paper towels. Serve hot on a bed of lettuce, with raw onion rings soaked in lemon juice, lemon wedges and ketchup.