- Melt the butter in a large pan over a medium heat, add the leeks and cook for 3-4 minutes until softened. Remove the leeks to a plate and set aside.
- Return the pan to the heat and add the mushrooms and ham. Cook for about 5 minutes or until the mushrooms are tender.
- Sprinkle in the flour and stir over the heat for a few minutes to get rid of any lumps before pouring in the stock. Bring to the boil then add the crème fraîche. Reduce the heat to a gentle simmer and cook for a few minutes until the sauce reduces and thickens.
- Remove from the heat and stir in the turkey with the reserved leeks. Season, stir through the parsley and set aside. The filling can be cooled completely and kept for a day in the fridge before topping and baking.
- Preheat the oven to 200°C/Fan 180°C/Gas 6. Transfer the filling to a medium pie dish, mounding it up slightly in the middle.
- Roll out the puff pastry on a lightly floured surface so that it is large enough to comfortably cover the pie dish and is about the thickness of a £1 coin.
- Cut a thin strip from one edge of the pastry (about 1.5cm wide) and press this around the edge of the pie dish. Brush this with the beaten egg then lift the pastry sheet over the pie to cover, pressing it around the edges.
- Trim the excess pastry with a small, sharp knife and crimp the edges together to seal. Make a small hole in the centre of the pastry lid to allow steam to escape.
- Glaze the top of the pie with the egg (you could decorate the pie with shapes made from the pastry trimmings at this point) then bake for 40-50 minutes or until the pastry is crisp and golden and the filling is piping hot.
Tips: To encourage the pastry to rise as much as possible, ‘knock up’ the edges of the pastry by pressing horizontal lines into the pastry rim all the way around the rim – these groves will help the pastry lift in the oven. Cooking from chilled will also help, as the pastry can firm up before cooking, just ensure the filling is fully heated through before serving.
You could also make this recipe with leftover roast chicken, or substitute chopped bacon for the leftover ham.