Ingredients
- 2 small potatoes (about 300g/11oz), cut into 1cm cubes
- knob of butter
- 2 small leeks, tough outer leaves removed, split in half lengthways and finely sliced
- 3 thyme sprigs, leaves chopped
- 1 tbsp Dijon mustard
- 2 tbsp cream
- flour, for dusting
- 500g block shortcrust pastry
- 140g/ 5oz Welsh Caerphilly cheese, strong cheddar or vegetarian alternative, cut into small chunks
- 1 egg, beaten