- Bring the stock to the boil and add the chicken breasts and cook for 10 to 15 minutes depending on the size of your breasts.
- In a large frying pan on a medium heat, add the bacon to the pan and render out the fat, removing it with a spoon. Cook till the bacon goes golden, not crispy. Put on to a plate with kitchen roll to absorb more fat.
- Remove the chicken from the pan and place on a board or plate to cool. Measure 200ml of the chicken stock, reserving anything remaining for something else. Leave the stock to cool for a little bit and add the milk; you should now have 500ml of liquid.
- In a saucepan melt the butter slowly, do not brown, Add the flour and mix in to form a paste (this is a roux) and cook it out for a few minutes. Adjust the heat slightly higher, then add the stock-milk mixture a little at a time, whisking a lot till you've added roughly half. Turn up the heat to a simmering heat, still whisking, especially the bottom as it does love to stick. Once it starts to thicken, continue adding the remaining liquid. Simmer till thickened to the consistency of a custard. Add the mustard and chopped chives and turn of the heat. Season with salt and pepper.
- Preheat the oven to 170 C / Gas 3.
- Roughly chop up the chicken to even-ish sized pieces, then add to the sauce along with the bacon, stirring to combine. Leave to cool.
- Roll out the pastry to the thickness of a pound coin and line your pie dish. I use 11cm foil ones, and get 4 out of this mixture. Blind bake for 10 minutes in the preheated oven, then take them out and add the filling. Crimp on the lid, brush with egg, make a slit on top of the pie, then return to bake in the oven for 25 minutes at 200 C / Gas 6, or till golden brown.
- Serve with some boiled baby potatoes and green beans with a little sea salt on top.
To make it slightly healthier you can substitute the butter for margarine, but not not that light marg, its mainly water so it just evaporates while melting for the roux. You can skim of the fat from the stock after you have cooked the chicken, when it's in the jug, use a ladle slowly putting it in and you should get all the fat that way.
Gluten free tip
To make it gluten free, use potato starch in the roux, and make your own gluten free pastry.