Preheat oven to 180°C. Melt the butter in a frying pan and then add the diced chicken in. Fry until the meat coloured. Pour out and set aside.
Add pancetta and chopped leek in the frying pan and cook for 5 minutes until the leek soften.
Put the diced chicken in.
Add plain flour in.
Add in chicken stock and creme fraiche and then add a little bit black pepper.
Put the leek mixture into a pie dish. Place the puff pastry on the top. Crimp the edges and cut a small hole on the top. Brush some egg on the pastry. Bake the pie for roughly 20-25 minutes until pastry has turned to golden brown. Enjoy.
