This comforting, Autumnal pie is a great way to use leftover chicken from the Sunday roast - hence the name! The pie can be made the day before up to the point of baking it in the oven. Ensure the ingredients have cooled to room temperature, then keep in the fridge. Allow it to come up to room temperature before baking.
Using the medium bowl of your food processor fitted with the adjustable slicing disc set to fairly thin, start the processor. Feed the leeks through the feeder tube to slice thinly. Melt the butter in a medium-sized saucepan, add the leeks and cook over a gentle heat for 10-15 minutes until softened, stirring occasionally. Off the heat, stir in the flour, followed by the stock, milk, cream or creme fraiche, mustard and seasoning. Bring to the boil, simmer for 10 minutes then remove from the heat.
Using the large bowl with the large blade, add the ham, chicken and parsley and Auto Pulse to chop into small chunks.
Add the ham, chicken and parsley to the sauce then tip into the pie dish and leave to cool a little.
Pre-heat your oven to 220C/425F/Gas 7.
Roll the pastry out onto a lightly floured surface to 5cm bigger than the pie dish. Cut a 2.5cm strip of pastry and place it round the rim of the dish. Brush it with the beaten egg, then lay the pastry over the top, trimming the excess and pressing down the edges. Crimp the edges, poke a hole in the middle of the pie with a fine skewer to allow the steam to escape, decorate with pastry leaves around the hole. Brush all over with egg.
Place on a baking sheet and bake for 20-25 minutes until the pastry has risen and turned golden brown. Serve piping hot.