Deep dish chicken tarragon pie

For the chicken
8 free-range chicken thighs on the bone (about 1.25kg)
1 med carrot, peeled and roughly chopped
1 onion
8 peppercorns
2 bay leaves, thyme srpigs and parsley stalks

for the rest of the filling:
4 med onions
a little butter and olive oil for cooking
8 rashers smoked streaky bacon
350g chesnut mushrooms
50g butter
50g flour
750ml chicken stock (from simmering the chicken pieces)
a small bunch of chopped parsley
4 tb tarragon leaves, chopped
1/2 x 500g block all-butter puff pastry
a little beaten egg and milk
23cm-24cm diameter pie dish, 5cm deep.

put the chicken thighs in a large heavy-based pot with the carrot, the onion, halved but unskinned, the peppercorns, bay leaves, thyme and parsley stalks. Cover with just over 2 litres of water and bring to the boil. Turn the heat down and leave to simmer for 30-45mins, or until the chicken is cooked and the water has become a tasty stock.

make the rest of the filling: peel the onions and roughly chop. Cook them slowly in a heavy pan with a little butter and olive oil, leaving them to soften and turn the palest gold. Remove the ring from the bacon, then cut it into short pieces and stir them in. cut the mushrooms into quarters and stir them in with the onions, letting it all cook until silky soft, yet barely coloured.

Strain the stock into a bowl, discard the stock flavourings. take the chicken off the bones, discard the bones and skin. keep the chicken pieces as large as you can, then set them aside. add the 50g butter to the onions and mushrooms, then the flour, stirring over a moderate heat until they are a pale biscuit colour.

Pour in 750ml of the hot stock from the chicken then simmer for 10mins untli you have a rich sauce. Introduce the chicken pieces, the parsley and the tarragon. Season generously.

Preheat oven to 200. Roll out the pastry, cut long strips from each side and press them on to the rim of the dish using the egg and milk mixture to help the pastry stick. Cut the pastry to fit the top of the pioe and brush the rim with the egg mixture then lay the rolled pastry on top. Trim the overhanging pastry and princh the edges together firmly. Brush the pastry with egg mixture and cut 2 holes in the top to let out the steam. Bake 35-40mins until the pastry is golden and puffed.