This pie is great because it is so simple and can be made from a tin or good quality ham when you have very little else to feed a fair number of people.
Transfer to a bowl and then add all the other ingredients except the breadcrumbs. Preheat to 200c/400f, and put in a baking sheet. Roll out the larger disc of pastry to cove the bottom and sides with a few cm of overhang. Sprinkle the bottom with breadcrumbs, then fill with the mixture. Roll out the rest of the dough to make a lid. Fold the overhang over and seal by pressing down with the tines of a fork. Just before baking glaze the pie with the milk salt egg combo, and stab it here and there with the prongs of a fork to make steam holes.Bake at 200c/400f for 10 minutes, then turn it sown to 180c/350f and bake for a further 45 minutes. Leave the pie to cool at least 10 minutes, but 25 is better.