You’ll be glad of all that leftover turkey when you taste this delicious pie! It will also use up ham, gravy and a little sherry.
For the pastry, mix the flour and salt together. Rub in the 65g chilled butter. Gradually add enough water to form a dough.
Lightly dust the work surface with flour and roll the dough into a rectangle. Grate 60g of frozen butter over the bottom two thirds of the dough. Fold down the top third and fold up the top third as if folding a letter.
Turn 90 degrees and roll out again. Repeat, adding the remaining frozen butter and folding as before. Rest in the fridge for 30 minutes before using.
For the filling, melt the butter in a large frying pan over a medium heat and add the leeks to the pan with the orange juice, zest and sherry. Cover and cook gently for 6 minutes, stirring occasionally, until the leeks are just tender. Remove the lid and increase the heat. Reduce the liquid until you are left with a few spoons of the buttery liquid. Sprinkle the flour over the leeks and stir to mix evenly. Gradually add the stock and simmer for 5 minutes until the sauce has thickened slightly. Add the mustard, turkey and ham, and stir. Finally, add the tarragon and cream. Season to taste with a little white pepper and salt.
Place a pie funnel in the centre of a 1.2/1.5-litre pie dish. Pour the pie filling and sauce into the dish and allow to cool.
Preheat the oven to 200°C/180°C/Gas 6. Roll out the pastry on a lightly floured surface to about 5mm thick. Cut a 2cm strip of pastry. Brush the rim of the pie dish with egg wash, then place the pastry strip onto the rim and brush this with egg wash. Cut the remaining pastry a little larger than the dish. Position the lid over the filling and make a steam hole to expose the funnel. Press the edges to seal then trim away any excess. Re-roll any trimmings and make decorations. Brush the pastry with egg wash, arrange any decorations on top of the pie and brush these with egg too.
Bake for 35–40 minutes until the pastry is risen and golden, allow to cool slightly before serving.