There are fish pies, and there are fish pies: this one is a real winner made with plenty of chunky fresh fish, and a potato topping, rather than pastry. It is important that the fish is ‘barely cooked’ before making the pie to give it plenty of texture and bite.
Place the potatoes into a saucepan of cold salted water, bring to the boil and cook until very soft. Drain, and leave in the colander to extract as much liquid as possible. Push the warm potatoes through a ricer into a bowl and then beat in the butter, milk, cream and egg yolks. Season with salt and freshly ground black pepper and set aside.
Place the haddock into a shallow saucepan together with the milk, rosemary and onion, and poach it over a moderate heat for about 5 minutes. Remove the poached haddock from the milk with a slotted spoon and set aside. Strain the milk and set aside. When cool enough to handle, remove the skin from the haddock and flake chunkily.
Heat a frying pan over a high heat, add a splash of rapeseed oil and very quickly sear the scallops on each side – just enough to colour them.
Arrange all the fish, including the prawns, in the bottom of an ovenproof dish, roughly
Melt the butter in a saucepan and add the flour. Cook over a medium heat for a couple of minutes and pour in the strained milk, and with the pan still on the heat beat continuously until you have a thick béchamel-type sauce. Add the cream and heat again, stirring continuously. Remove from the heat and then carefully stir in the chopped eggs, capers, parsley and lemon juice and season with salt and freshly ground black pepper. Pour this mixture over the fish.
About 10 minutes before serving preheat the grill to high. Reheat the potatoes in a saucepan over a moderate heat and spread the topping over the fish. Place the fish pie under the grill for a couple of minutes to colour the potatoes. Serve immediately.