Here are the ingredients
Melt the butter in a large deep sided pan
Add the leeks and a teaspoon of garlic (optional). Cook for 3-4 minutes until softened. Stir occasionally
Add the mushrooms and increase heat to high. Stir fry for 2-3 minutes until slightly wilted
Add the wine to the pan and simmer until nearly all has evaporated
Reduce the heat to medium-low and stir in chestnuts, cream, lemon juice and half the thyme leaves.
Simmer gently for a few minutes until the sauce has reduced a little. Season to taste. Transfer to a dish to cool completely. Preheat oven to 190°C/fan170°C/gas 5
Meanwhile, toast some sesame seeds in a small frying pan
Roll out the pastry
Cut 4 discs of around 16cm, then cut a further 4 of around 11cm. You will need to re-roll to achieve this
Lay the large pastry discs on a lined baking sheet and divide the cooled mixture between them, spreading to an even layer but leaving a border round the edge of each
Brush the borders with the beaten egg then lay the smaller discs over the filling and brush with beaten egg
Bring up the pastry borders and pinch into the top pastry to form a seal.
Brush with the egg glaze and sprinkle with a little thyme and the toasted sesame seeds.
Make two small steam holes in the top of each. Then they are ready for the oven. Bake for 25 minutes or until the pastry is golden brown and the filling is piping hot (Cook at 190°C/fan170°C/gas 5)
Serve with your favourite green vegetable.