Welsh Leek & Bacon Pasty (Pastai Cennin)

Pre-heat oven to 180°C (350 F).
Turn short crust pastry dough onto a lightly-floured work surface and cut in half. Roll the two halves out until they are the same size as dinner plates.
Lay one round of dough on a lightly-greased baking sheet then scatter the leeks over the top (leave the edges of the pasty clear, however).
Lay the bacon on top of the leeks then season with salt and black pepper before dotting the butter on top.
Spread parsley, sage and egg over bacon and leek, leaving edges of pasty clear.
Lightly brush around edge with egg/milk glaze.
Lay the second piece of pastry on top then crimp down the edges with the tines of a fork to seal.
Brush glaze over top crust.
Prick the top of the pasty with the fork to make steam holes.
Transfer to an oven and bake for about 40 minutes, until the pastry is golden and the contents are cooked.