Ingredients 1kg Maris piper or white potatoes 400ml of semi-skimmed milk or milk alternative 25g butter 25g plain flour 4 spring onions 300g cod loin 300g arctic char or salmon 200g haddock 200g king prawns 1 tsp mustard 200g garden peas 70g reduced fat cheddar cheese Method Heat the oven to 200C/fan 180C/gas mark 6. Put 1kg potatoes, peeled and halved, in a saucepan and pour over enough water to cover them. Bring to the boil and then simmer until tender. When cooked, drain thoroughly and mash with a splash of milk. Season with ground black pepper. Put 25g butter, 25g plain flour and 4 finely sliced spring onions in another pan and heat gently until the butter has melted, stirring regularly. Cook for 1-2 mins. Gradually whisk in 400ml milk using a balloon whisk if you have one. Bring to the boil, stirring to avoid any lumps and sticking at the bottom of the pan. Cook for 3-4 mins until thickened. Take off the heat and stir in the fish, mustard, and chives Spoon into an ovenproof dish Spoon the potato on top and sprinkle with a handful of grated cheese. Pop in the oven for 20-25 mins or until golden and bubbling at the edges. Alternatively, cover and freeze the pie for another time.