Put the grated onion in a pan with just enough milk to cover. Simmer for 5 minutes then add the fish and poach gently for 5 more minutes. Turn off the heat and cool.

Strain the milk into another pan. Add the potato, cook until tender, then drain reallly well.

Tip the fish and onion into a bowl. Flake the fish and discard any skin and bone.

Mash the fish with the potatoes, lemon zest, dill, flour and egg and season well. Scoop the mix out in rough tbsps and put on a tray. Chill in the fridge for 30 minutes, or until you want to cook them.

Heat 1cm of oil in a frying pan. Cook the fritters in batches until golden brown and crisp on both sides. Keep warm in a low oven while the others cook. Serve with lemon wedges.