Bring a saucepan of water to the boil and cook the potatoes with their skins on for about 10 minutes. Drain and leave to cool for a few minutes.

Meanwhile, finely chop the salmon or cod fillet and place in a bowl. Stir in the chopped spring onions, grated root ginger, chopped coriander and lemon juice. Season to taste with salt and cayenne pepper.

When the potatoes are cool enough to handle, peel off the skins and grate the potatoes coarsely. Gently stir the grated potato into the fish mixture.

From the fish mixture into 12 cakes, pressing the mixture together but leaving the edges slightly rough.

Heat the oil in a large frying pan, and, when hot, fry the fish cakes a few at a time for 3 minutes on each side, until golden brown and crisp. Drain on kitchen paper. Serve hot with lemon wedges for squeezing over. Garnish with sprigs of fresh coriander.