Using a large, heavy bottomed frying pan or sauté pan on a low to medium heat, add 2 tablespoons of olive oil and the butter, add the onion and bacon and cook gently until they soften and start to lightly brown.
Add the chicken mince, stirring regularly, until it’s cooked through.
Sprinkle the mixture with flour and stir cooking for another minute. Pour in the chicken stock and milk, add the corn and parsley, stir until sauce starts to thicken.
Season with salt, then cook for another 4-5 minutes stirring continuously until the sauce has reduced slightly and is thick.
Remove from the heat, transfer to a glass or ceramic dish, cover and set aside, allowing to cool totally (about 30-40 minutes).
Preheat oven to 220°C. Defrost the pastry and cut each square of pastry in a half. Place about 2 heaped tablespoons of the cooled chicken mix, a 3rd of the way down each pastry rectangle (allowing about 2.5 cm clear around the edges). Wet the edges of the pastry with a little water fold over to cover the filling and form a square. Use a fork to crimp the edges together to seal. Cut a small hole in the top of each pie to allow steam to escape. Repeat with the remaining pastry sheets.
Place on the lined baking tray, lightly brush each pastie with beaten egg. Bake for about 20-25 minutes until golden brown. Makes 8.