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.
Preheat the oven to 180'C.
Melt the butter in a large saucepan over a medium heat and then add the flour. Once the flour and butter come together to form a ball, slowly whisk in the milk, mustard and nutmeg until you have a smooth sauce.
Add the spinach leaves and cook for a couple of minutes to wilt the leaves. 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 in cold water and then remove the shells. Cut each egg into quarters.
Remove any skin and bones from the fish and cut the meat into 1 inch pieces. Place the fish in the bottom of your pie dish, add the eggs and the pour the spinach and white cream sauce on top. Season with salt and pepper.
Beat the egg to make an egg wash. Brush around the edge of the pie dish and then place the shortcrust pastry on top of the pie. Press the pastry down and trim away the edges. Brush the top of the pastry with egg wash and then transfer to the oven and bake for 20-25 minutes or until golden brown.
«If you have time, rest the dough for 24hrs before rolling. This will make it easier to handle.»