Preheat the oven to 180°C/ 350°C/gas mark 4. Grease the Pyrex 4 Cup Bun/Yorkshire Pudding Tray dish.
Turn out the ready rolled pastry onto a floured surface and using a 12cm round cutter make 4 circles to form the base of each pie. Take a 10cm round cutter and cut a further 4 circles which will create the lids. Line the Pyrex 4 Cup Bun/Yorkshire Pudding Tray with the 12cm pastry circles ensuring a rim is left on each pie.
Heat the readymade creamy mushroom sauce.
In a saucepan, sauté the sliced leeks over a medium heat with a knob of President Butter until softened, taking approximately 5 minutes.
Add the sautéed leeks, the shredded chicken and the cooked ham to the heated sauce and season to taste. Generously spoon the filling into the Pyrex 4 Cup Bun/Yorkshire Pudding Tray so that the surface of the filling is slightly rounded.
Place the lids on top of the individual pies pressing the edges of the pastry together to seal the pies. Crimp the edges by pushing your thumb into the rim of the pastry and, using the thumb and forefinger of the other hand, gently pinch the pastry so that it is pushed up by this action. Continue around the edges of each individual pie.
Using the tip of a sharp knife make a few slits in the lid of each pie, so that the filling is visible, and glaze the pies with egg wash. Bake in the oven for 20 to 25 minutes until the pastry is golden.