Preheat the oven to 200C/400F/Gas 6.
Heat the oil inside a fry pan, add some chicken and fry before the chicken starts to turn white-colored.
Add some mushrooms and then fry before the chicken is golden-brown.
Take away the chicken and mushrooms in the pan and hang aside. Add some onion and garlic clove towards the same pan and fry for just two-3 minutes or until softened. Remove in the heat and hang aside using the chicken and mushrooms.
Melt the butter inside a saucepan, stir within the flour and prepare for around three minutes, stirring constantly until it's created a thick smooth paste (this really is known as a roux).
Mix the milk and stock together inside a jug, adding the nutmeg, white-colored pepper and salt, to taste. Pour the liquid gradually in to the flour mixture, whisking constantly until smooth. Simmer on the gentle heat, stirring constantly, for around 5 minutes or before the sauce has thickened.
Stir within the chopped parsley and pour the sauce within the chicken and mushroom mixture. Mix well, then spoon right into a cake dish and then leave until completely awesome.
Unveil the pastry on the gently floured surface until it's the thickness of the pound gold coin. Brush the perimeters from the cake dish with beaten egg, lay the pastry on the top, press lower the perimeters and trim. Brush the top cake with beaten egg and cut some leaf shapes from the left-over pastry to brighten the top cake.
Make 2 or 3 slits in the top cake to permit steam to flee after which bake within the oven for 25-25 minutes or until golden-brown on the top.