Place the chickens into a pot along with the leeks, carrot, onion, peppercorns and bay leaves.  Cover with water and bring to the boil and simmer for an hour or until the chicken is cooked, then remove from the heat and allow to cool.

When the chicken has cooled remove from the pan, reserving the liquid and remove as much meat as possible, then set aside.

Pre heat the oven to 200ºc.

In a large pan melt the butter over a medium heat and whisk in the flour.  Combine to make a roux paste, then gradually add 500g stock from the pan used to cook the chicken.

In another pan melt the butter over a medium heat and add the baby onions and water chestnuts and cook for a couple of minutes.

Place the chicken, baby onions, water chestnuts and tarragon into the sauce and mix thoroughly.  Transfer into a large pie dish.

Brush the edge of the pie dish with egg wash then place the pastry over the chicken mixture and crimp the edges.  Brush the pastry with egg wash, pop onto a baking tray and bake for 30 minutes until golden brown.