Method

1. Melt 40g of the butter in a saucepan and add the flour. Stir this over a medium-low heat for 1 min to make a roux. Remove from the heat and start adding the cider a little at a time. Mix well with a wooden spoon to ensure there are no lumps. Keep stirring until all the cider has been added, then add the milk in the same way. Season, return the pan to the heat and, stirring continuously, bring to the boil. The mixture will thicken considerably and, once it has come to the boil, reduce the heat and simmer for about 3 mins. Stir in the mustard, lemon juice and crème fraîche , and taste for seasoning.

2. Melt the rest of the butter in a frying pan and gently fry the leeks and the apples for 5 mins. Add 2 tbsp of water, season, cover and cook over a low heat for 8-10 mins until tender. If there are lots of juices, increase the heat to reduce them.

3. Add the chicken and half the cheese to the sauce, then bring to the boil. Immediately reduce the heat and heat the chicken through. Gently stir in the leeks and apples and taste – you may want to add more mustard or lemon juice.

4. Put the mixture into a 25 x 20cm pie dish or a round dish measuring 25cm across (with a 1.3 litre capacity). Sprinkle with the rest of the cheese and leave to cool completely.

5. Heat oven to 200C/180C fan/ gas 6. On a lightly floured surface, roll the pastry out to the thickness of a 50 p coin. Cut off a strip the same width as the lip of the pie dish. Wet the lip and press this strip onto it. Brush the strip with water and lay the rest of the pastry on top. Press the pastry lid onto the pastry strip, then cut off the excess. Crimp the edges and use the remaining pastry to decorate the top of the pie. Make three small slits in the pastry near the middle to let the steam escape. Brush the top with the egg mixture and bake in the oven for 30 -40 mins, until the pastry is a deep golden colour and puffed up. Serve immediately.