Cheese and potato pie

Method

1. To make the pastry, put the flour and salt into a heatproof bowl, make a well in the centre, crack in the egg, then cover with the flour. Put the butter and lard in a pan with 200ml water and bring to the boil. When the fats have melted, pour the mixture onto the flour, mixing well with a knife. When cool enough to handle, knead the pastry on a floured work surface until smooth. Shape into a disc, cover loosely, then leave to cool for 20-30 minutes.
2. Meanwhile, cut the potatoes into small chunks, then cook in boiling water for 15-20 minutes until just tender. Drain and spread out on a roasting tin or tray to cool.
3. Once the pastry is lukewarm, cut off one third, wrap it in cling film and chill. Roll out the rest on a floured work surface to a circle just over 40cm in diameter, then use to line a greased 20cm loose- bottomed, 8cm deep cake tin. There should be 2-3cm of pastry overhanging – if you don’t have enough, work the pastry up from the base to stretch it gently over the sides. Chill the lined tin.
4. Heat the oven to 220°C/200°C fan/ gas 7. Once the potatoes have cooled completely, mix them with the other filling ingredients (except the whole egg) in a bowl. Season, taste, then adjust the seasoning.
5. Remove the lined tin from the fridge and pack the potato mixture into it. Roll out the reserved pastry on a floured surface to fit over the pie, then brush the overhanging edges round the tin with the beaten egg yolk and put the lid on top.
6. Squeeze together the edges of the pastry lid and overhang to seal, then use scissors to trim most of the excess, leaving enough to crimp the edges. Crimp either with a wooden spoon handle and fingers, or with a fork. Cut a steam hole in the top and use off-cuts to decorate the pie, if you like. Beat the whole egg, then brush it twice over the top of the pie to glaze.
7. Bake the picnic pie for 30-35 minutes until the top is deep golden and crisp. Leave to cool to just warm or room temperature, then slice and serve.