Preheat oven to 180°C/356°F.

Dice up your chicken thighs into chunks. Brown them off in a large pan with some olive oil. Remove the chicken from the pan and set aside.

Finely slice your leeks, bacon and onions.

Add bacon to the chicken pan, and fry until crispy. Deglaze the pan with a splash of water, and then add the leeks and onion.

Fry until soft, adding splash of water if the vegetables start catching on the pan.

Once soft, re add the chicken. Stir it in, and then add a large handful of chopped tarragon. Stir, and then add 2 heaped tablespoons of flour.

Mix it in, making sure the flour is absorbed by the mixture, and then pour in a pint of milk, splash by splash. Keep stirring until you have a thick pie filling. Season generously with
pepper, and then remove the pan from the heat.

Take a pie dish. Fill it with the filling. Then lay your puff pastry on top. Trim the sides, and brush the pastry with egg yolk wash. Add a sprinkle of salt, and then place in the oven
for 30 minutes, or until the pastry is puffed up and golden.

Slice your pie up, and serve with a big dollop of Dijon mustard. Enjoy!