Step 2

Melt 1oz of butter in a large heavy-based saucepan over low heat. Add the leeks and fry gently for 2 minutes, stirring, until just softened. Add the garlic and cook for 1 further minute.

Step 3

Add the remaining filling butter and stir in the flour as soon as it has melted. Cook the roux for 30 seconds, stirring constantly.

Step 4

Gradually add the milk a little at a time, stirring well between each addition. Then gradually add 1 cup of the reserved stock and the wine (if using), stirring until the sauce is smooth and slightly thickened. Bring to a gentle simmer and cook for 3 minutes.

Step 5

Season with salt and pepper. Remove from the heat and stir in the cream. Pour into a large bowl and press plastic wrap onto the surface to prevent a skin forming. Set aside to cool.

Step 6

Heat the oven to 400°F and put a baking sheet in it to heat.

Step 7

Make the pastry: put the 12 1/4oz flour and 7oz cold butter in a food processor and pulse until the mixture resembles fine breadcrumbs. With the motor running, add the beaten egg and 1 tablespoon cold water; blend until the dough forms a ball. Set aside 8 3/4oz of pastry for the lid.

Step 8

Roll out the remaining pastry on a lightly floured surface to about 5mm thick and 4cm larger than the pie dish. Lift it over a rolling pin and lower into the dish. Press firmly up the sides without air bubbles, leaving the excess overhanging the edges.

Step 9

Cut the cooked chicken into 3cm pieces. Stir the chicken, ham, and leeks into the cooled sauce. Pour the filling into the pastry-lined dish. Brush the rim with beaten egg. Roll out the reserved 8 3/4oz of pastry and lay it over the top as a lid. Press the edges together firmly to seal and trim any excess.

Step 10

Make a small hole in the center of the lid with a knife tip. Glaze the top with beaten egg. Bake on the preheated tray in the center of the oven for 35–40 minutes, until golden-brown all over and the filling is steaming hot.