When you turn the pie out of the tin it resembles a cottage with subsidence. Word of warning: you want everyone at the table before you put your knife into the pie.
Don’t let the dough go cold or it will be difficult to use. The quantity given here makes enough for two goes, just in case.
To make the dough, place the flour, eggs, egg yolk, melted butter and salt in the bowl of an electric mixer. Using the beater attachment, mix the ingredients to a firm paste. Add the water and mix again until a soft, glossy, pliable dough is formed. Cover the bowl with a cloth and leave in a warm place for 30 minutes.
While the dough is resting, cut the potatoes into slices 1cm thick and do the same with the Wigmore cheese. Grease a 9 x 5 x 3-inch loaf pan with butter and then dust it with flour.
Roll out half the pastry very thinly—about 1/10 inch thick. Try to do this quite quickly so it doesn’t go cold. Use the rolled-out dough to line the loaf tin, making sure you have about ¾ inch overhanging; trim off the rest. Cover the base of the pastry with some of the sliced potatoes—you will have to trim them a little—then season with salt and pepper. Add a layer of Wigmore cheese. Carry on layering until you reach the top of the tin, ending with a layer of potatoes.
Roll out a lid for the pie from the dough trimmings. Place the lid on top of the potatoes, then brush the overhanging dough with the beaten egg and fold it over the pastry lid to seal. Brush the top with more egg.
Place in an oven preheated to 350°F and bake for about 1 hour, until golden brown on top and piping hot in the middle. Serve with pickled walnuts.