1. Cook the potatoes in boiling water for 10-15 minutes until tender. Drain thoroughly, return to the pan and mash. Boil the eggs for 8 minutes then run under cold water, peel and chop. While the potatoes are cooking place the haddock in a shallow pan, cover with cold water, bring to the boil and poach for 8-10 minutes until just cooked through and opaque. Remove and flake the flesh.
2. Cook the leeks in the butter in a medium frying pan for 4-5 minutes until soft then stir into the potato mixture with the lemon juice. Fold through the flaked fish, eggs and chopped capers. Season to taste. Shape the mixture into 8 patties. Place the flour in a shallow bowl and dip the fishcakes in it to coat lightly. Chill until needed.
3. To make the sauce: melt a small piece of the butter in a pan and add the shallots. Cook gently until soft but not golden, then add the white wine and boil until reduced by half. Add the curry powder and cook for 1 minute, then add the cream and bring to simmering point. Gradually whisk in the butter in small pieces to give a smooth sauce. Check seasoning and add the parsley. Keep warm while you cook the fishcakes.
4. Heat the oil in a shallow non-stick frying pan and fry the fishcakes for 6-8 minutes until golden brown, turning once. Drain on kitchen paper and serve with the sauce and a green vegetable of your choice.