Ingredients

• 350g/12oz plain flour
• 200g/7oz butter
• chilled
• pinch salt
• 1 free-range egg yolk
• chilled water
• 50g/1¾oz butter
• 2 leeks
• sliced
• 350g/12oz mushrooms (such as chestnut or button mushrooms)
• 2 garlic cloves
• sliced
• large sprig thyme
• leaves only
• 15g/½oz dried mushrooms (optional)
• soaked in 150ml/5fl oz freshly boiled water
• 50g/1¾oz plain flour
• 1 tsp Dijon mustard
• 100ml/3½fl oz marsala
• 200–300ml/7–10fl oz vegetable or chicken stock (amount depending on whether or not you are using dried mushrooms)
• 200g/7oz vacuum-packed chestnuts
• left whole

Directions

• To make the pastry
• either put the plain flour and butter into a food processor with a generous pinch of salt and pulse until it resembles breadcrumbs
• or rub it in by hand. Add all but a tablespoon of the egg yolk and just enough chilled water to bind it together. Shape into a ball
• wrap in cling film
• and chill in the fridge until you are ready to roll it. Reserve the remaining egg yolk for egg wash later.
• To make the filling
• put the butter in a large saucepan and melt over a low heat. Add the leeks and cover. Fry for 5 minutes.
• Turn up the heat slightly and add the mushrooms. Cook for a further 4–5 minutes
• then add the garlic and thyme. If using
• drain the rehydrated mushrooms
• reserving their soaking liquor
• and roughly chop. Add to the saucepan.
• Add the flour and stir until you can see a roux has formed around the vegetables.
• Stir in the mustard
• then add the marsala and stir until it is well incorporated. Gradually add the stock and the mushroom liquor
• if using. (If not using the mushroom liquor
• use the larger quantity of stock.) Bring the mixture to the boil
• then turn down and simmer
• continuing to stir
• until it has thickened. Add the chestnuts
• cover
• and remove from the heat. Leave to cool.
• Preheat the oven to 190C/170C Fan/Gas 5.
• Divide the pastry into two pieces
• one slightly bigger than the other. Roll out the larger piece of pastry and use it to line a pie dish. Add the cooled filling.
• Roll out the remaining piece of pastry and top the pie
• wetting the edges with the egg wash
• making sure they are well crimped together. Cut a couple of slits in the pie to let steam escape and brush with egg wash.
• Bake in the oven for around 40–45 minutes
• or until the crust is golden brown. Serve in slices.