Cook the potatoes in salted water over a medium heat for approx. 15 mins. until soft. Drain the potatoes and allow the water to evaporate, pass through a food mill into a bowl. Mix in the fish and spring onion, season. Divide the mixture into 16 portions, shape into burgers. Pour the cornflakes into a shallow dish, roll the burgers in the cornflakes.
Preheat the oven to 60°C, warm the platter and plates.
Heat the oil in a non-stick frying pan. Fry the burgers in batches for approx. 5 mins. on each side, keep warm in the oven.
Mix the yoghurt with the ketchup, mayonnaise and parsley, season. Serve the dip with the burgers.