Make sure the butter and water are cold before making the pastry.
Finely dice the butter, add it to the flour and rub with your fingertips until the mixture resembles fine breadcrumbs. Make a well in the centre of the bowl and add most of the water and a pinch of salt.
Mix the dough without overworking it. You just want to bring the ingredients together.
Roll the mixture into a ball, flatten slightly and cover with cling film. Allow to rest in the fridge for at least 30 minutes. When you are ready to top the pie, roll the pastry out to a thickness of 5mm. Brush the edges of the pie dish with egg wash and place the pastry on top. Trim the edges and score a pattern in the top if desired.
Preheat the oven to 180'C.
Melt the butter in a large saucepan over a medium heat. Once melted, add the flour and mix until well combined. Slowly add in the milk followed by the mustard and the nutmeg. Whisk well to give a thick sauce - the texture should resemble double cream.
Wash and drain the spinach and then add to the sauce. Cook for a minute or two to wilt the spinach leaves and then remove from the heat.
Bring a small saucepan of water to the boil, add the eggs and cook for 4 and a half minutes. Refresh the eggs in cold water to halt the cooking process. Remove the shells and cut each egg into quarters.
Remove any skin and pin bones from the salmon and then cut the meat into 1cm dice before adding to a pie dish. Peel and de-vein the prawns and add to the dish. Cut the scallops in half and add to the dish. Add the egg, season with salt and pepper and the pour the spinach sauce over the top.
Brush the edges of the pie dish with a little beaten egg and then lift the pastry and place on top. Trim the edges and then brush the top of the pastry with the egg wash.
Bake the pie in the oven until crisp and golden brown - 20 to 25 minutes.
«For best results, use fresh seafood in this dish but defrosted fish pie mix will also work perfectly well.»