Put the chicken pieces into a large saucepan, together with the half onion, peppercorns and herbs and pour enough milk just to cover the chicken.

Bring to the boil, then, just when it starts to bubble, lower the heat and leave to simmer, partially covered by a lid for about twenty minutes.

Remove the chicken from the poaching liquid, reserving the milk.

Once the chicken isn’t too hot, pull off the skin and cut the meat off the bone into small, plump pieces.

Preheat the oven to 200°C.

Slice the bacon into small pieces and the leeks into thin half moons.

Melt the butter in a large saucepan and add the bacon. The bacon should soften without colouring over a moderate to low heat.

Add the leeks to the bacon and continue cooking for about fifteen minutes more, until the leeks are totally soft.

Stir the flour into the leek and bacon, continue cooking for a couple of minutes.

Gradually strain in enough of the warm milk to make a thick sauce.

Season generously with salt and pepper.

Unroll your first sheet of puff pastry onto a lightly floured surface. Roll it out to about 10.5 x 14.5 inches.

Place it on a baking sheet. Spoon the filling onto the pastry, leaving a wide rim all the way around.

Brush the rim with the beaten egg and milk.

Roll out the second piece of pastry to the same size as the one before and lower it over the filling.

Press and crimp the edges together firmly to seal them.

Brush the pastry all over with the beaten egg wash and bake for 35 minutes or until golden brown.