Creamy chicken, mushroom and dijon pie

Method

1. Put the chicken in a stock pot or large deep casserole with the carrot, celery, chunks of onion, bay leaves, peppercorns and a large pinch of salt, then cover with water.
2. Bring to the boil, then turn the heat down and poach the chicken, turning halfway through, for 1 hour or until tender and cooked through (it should read 72°C at the thickest part of the thigh on a digital probe thermometer; the juices should run clear when the thigh is pierced with a skewer). Once cooked, remove the chicken and set aside until cool enough to handle. Reserve 600ml of the stock (chill or freeze the rest to use for soups or stews). Shred the meat from the carcass in generous chunks, discarding any skin and bones. Set the meat aside to cool completely.
3. Heat 25g of the butter in a frying pan, fry the chopped onion for 5 minutes until beginning to soften, then add the fresh mushrooms and fry over a high heat until golden brown.
4. Put the remaining 75g butter, the flour, wine and 600ml reserved poaching stock in a saucepan set on a medium-high heat, stirring continuously, until thickened. Stir in the cream, mustard, soaked porcini and their soaking liquid (discard any grit), herbs, the fried mushrooms and the shredded chicken. Season with salt and pepper, then spoon into the pie dish and leave to cool (or see Make Ahead ).
5. Meanwhile, make the pastry by sifting the flour and a pinch of salt into a bowl and adding the butter. Using your fingertips, rub in the butter until it resembles fine crumbs. Sprinkle with 3 tbsp cold water, then stir with a knife until the mixture clumps together – add a tiny bit more water if it’s dry. Bring the mixture together into a rough ball. Tip out onto a lightly floured surface and knead briefly to form a smooth, firm dough – don’t overwork it or you’ll end up with tough pastry. Wrap in cling film and chill for 30 minutes.
6. Heat the oven to 200°C/180°C fan/gas 6. Roll out the pastry on a lightly dusted surface to the shape of your pie dish. Use the offcuts to make a strip and stick it around the edge of the dish. Lay the pastry lid on top, then crimp the edges and make a steam hole in the middle. Use any remaining pastry to make stars to decorate the top, if you like, then brush all over with beaten egg to glaze.
7. Bake for 45-50 minutes until the pie is piping hot and the pastry is golden and crisp.