Heat oven to 220C/200C (fan), and line baking tray with baking paper or tin foil.

In a medium sized saucepan, melt the butter over a medium heat. Crush the garlic, and add it to the melted butter. Finely slice the leek, and add it to the pan. Cook for around 6-8 minutes until soft. Meanwhile, dice the chicken breast into 1 inch cubes.

When the leek is soft, add the diced chicken breast to the pan, and cook through until no longer pink. While the chicken is cooking, add the cold water to the cornflower in a small bowl or mug to form a paste.

When the chicken is no longer pink, add the wine to the saucepan, followed a few minutes later by the stock. Cook for a further 5 minutes.

Add the cornflour paste to the saucepan with salt, pepper and dried parsley to season. Mix through and remove from the heat.

Take the first sheet of puff pastry and place on chopping board or other flat surface. Leaving a 1.5 inch border around all sides, make about 8 evenly spaced slits along the sheet. This will be the pie lid.

Place the second sheet of pastry directly onto the baking tray. Spoon the chicken mixture into the centre, leaving the same 1.5 inch border around the edges.

Slice the brie, and add the slices to the top of the chicken mixture.

Beat an egg, and brush the beaten egg around the 1.5 inch border on the second sheet.

Place the pie lid (first sheet) on top of the second. Press down the border with your fingers, and crimp the edges to seal in the melted cheese.

Brush the remaining beaten egg over the lid, and cook for 15-20 minutes until the pastry is golden brown. Let it stand for a few minutes before serving.