Preheat the oven to 180C/gas 4. Grease a 26cm x 20cm pie dish with butter, then on a lightly floured surface, roll out a third of the pastry to the side of the top for the pie, using the dish as a guide and going a little larger, then chill. Roll out the remaining pastry and line the dish with it. Make a few pinpricks in the bottom with a fork. Chill, cling filmed, for 15 mins, and then bake for 5 mins, covering just the bottom with an oval of tin foil.

Meanwhile, place the potatoes in a large saucepan of cold water and bring to the boil. Simmer for 10 mins, then drain and season with pepper.

Fill the pastry case with half the potatoes, leaving a couple of gaps. Add dots of the Branston Pickle, butter and half the Pilgrims Choice Mature cheese, then repeat the process with the remaining potatoes, butter, cheese and pickle. Top with the pastry lid and seal the edges by making a pattern around with the back of a fork, brush the top with the beaten egg. Bake for 25-30 mins, until golden and serve immediately or chilled.