Cook the potato slices in a large pan of boiling salted water for 2-3 mins until just tender. Drain, then spread out over a clean tea towel and leave to steam-dry. Once cool, combine with the cream, mustard and seasoning.

Heat the oven to 220C/200C fan/gas 7. Unravel one of the puff pastry sheets over a lightly floured surface and roll out so it’s slightly thinner. Cut out a 25cm circle. Spread the cranberry sauce over the pastry disc, then arrange half the potatoes on top in a neat circle. Scatter over the cheese and ham hock, then top with the remaining potatoes, patting the filling into a dome shape.

Roll the second pastry sheet out until it is 30cm wide, and cut out a 30cm circle. Lift this over the filling and smooth it over, pressing it down at the edge and easing out any air as you go. Crimp the edge together to seal, then cut a small air hole in the top and chill for 20 mins. Can be covered and chilled for up to 24 hrs before glazing and baking.

Brush the top of the pastry with the beaten egg yolk. Score lines all around the pithivier using the tip of a small sharp knife, starting from the steam hole and curving down to the edge. Bake for 30 mins until the pastry is golden and the filling is hot.