Instructions

1. Pre-heat the oven to 200°C/375°F/gas mark 6
2. To prepare the pie dish, roll out the block of all-butter puff pastry to a thickness of 1cm, to fit your pie dish.
3. Next, cut two thin strips off the edge of the pastry rectangle and stick around the four sides of the pie dish using a little lightly-beaten egg to glue it (you need this rim to successfully attach your lid) Now, place the lined pie dish and the rolled sheet of puff pastry in the fridge while you make the filling.
4. To make the chicken filling, chop the chicken breasts, onion, carrot and celery and into bite-sized pieces, and cover completely with the stock and the bay leaf. Place on a medium heat and simmer gently for 25-30 minutes, stirring occasionally.
5. Remove the chicken from the stock. Check the chicken is cooked by gently breaking a piece in half, it shouldn’t have any tinge of pink. Season and set aside on a warm plate.
6. Melt the butter in a heavy frying pan and once foaming add the sliced mushrooms and lemon juice. Fry for 4-6 minutes. Remove from the heat and allow to rest.
7. Add the cream to the chicken stock, bring the sauce back to a simmer and then add three quarters of the roux, whisking continuously as you add it in. Simmer gently for 5 minutes or until you have a thick sauce, adding the remaining roux if needed. Gently mix in the cooked chicken pieces and the mushrooms, add the chopped herbs and season.
8. Place the chicken mixture in the prepared pie dish and allow to chill for 1 hour in the fridge before carefully placing the rolled out sheet of puff pastry on top. Allow it to settle a little before pressing down gently on the pastry rim you made earlier.
9. Trim off the excess pastry from around the edges and, using the same sharp knife, crimp the pastry edges with small sharp indentations. Pierce the centre of the pie with the sharp tip of the knife to allow air to escape. For the very best result return the pie to the fridge for at least an hour (6-8 hours is fine).
10. Then remove from the fridge and carefully brush the pastry lid with the remaining egg wash, being careful not to get any on your carefully crimped edges, then immediately place in a very hot oven to bake for 30-40 minutes, by which stage the pastry will be golden, flaky and crisp and the creamy filling will be bubbling and delicious.