Boil the potatoes in a saucepan with enough water to cover for 15 to 20 minutes or until tender. Drain well, then mash. Set aside to cool.
Meanwhile, place the fish in a shallow pan with enough cold water to cover and add half the juice of 1 lemon. Bring to the boil, reduce the heat to low and simmer for 1 minute. Remove from the heat, cover pan and leave to cool for 4 minutes. Drain the fish and flake the flesh with a fork, discarding any skin and bones.
Mix together the potatoes and fish with a fork, adding the 1/2 teaspoon cumin, the 1/2 teaspoon paprika, hot sauce, spring onions, garlic, coriander, ginger and the remaining 1/2 juice of 1 lemon.
Tip the flour onto one plate, the eggs onto a second plate and the breadcrumbs onto a third plate. Take about 1 tablespoon of the fish mixture and shape into a fishcake. Turn first in the flour, then dip into the egg and, finally, coat with crumbs. Shape and coat the remaining fishcakes in the same way, making 24 all together. Chill the fishcakes for 1 hour.
Heat half the oil in a nonstick frying pan. Add half the fish cakes and cook over medium heat for about 3 minutes on each side or until golden. Remove and keep warm while you cook the rest of the fishcakes, using the remaining oil.
For the dipping sauce, stir together the mayonnaise, yoghurt, the 1/2 teaspoon paprika, the 1/4 teaspoon cumin, lemon juice and mint. Serve with the fish cakes.