Instructions

1. Preheat the oven to 200°C/ fan 180°C/gas mark 6.
2. Add 1tbsp olive oil to a large frying pan, over a high heat. Add the chicken, season with a little salt and pepper, and fry for about 10 minutes, until cooked through. Remove to a plate.
3. Add a little more olive oil to the pan and turn down the heat to low. Add the onion and cook gently for about 5 minutes.
4. Push the onion to one side of the pan and add the butter along with the flour. Using a wooden spoon, stir until combined, for about 2 minutes, over the heat.
5. Gradually add the chicken stock, whisking all the time using a hand whisk. Once combined, gradually add the wine and then the milk. Leave the mixture to simmer over a low heat for about five minutes.
6. Meanwhile, add a knob of butter to a medium-sized saucepan and fry the mushrooms over a high heat for about five minutes.
7. Add the cooked mushrooms to the saucepan, along with the cooked chicken.
8. Transfer to a large pie dish. Roll out the pastry and cut to match the shape of the dish. Wet the lip of the dish with a little water. Carefully lift the pastry lid onto the pie dish and pinch the edges to the dish. Glaze with a little beaten egg and pierce a small hole into the centre of the pie to allow steam to escape.
9. Place the dish on a large baking tray, in case of sauce bubbling over during cooking, and bake in the preheated oven for 30-35 minutes.