Chicken, ham and mustard lattice pie

Method

1. To make the pastry, put the flour, salt and butter in the bowl of a food processor and pulse until the mixture resembles fine crumbs. Add the beaten eggs and 2 tbsp iced water and pulse until the mixture starts to come together into a ball, adding a little more water if needed. (Alternatively, put the flour and salt in a large mixing bowl and rub in the butter until the mixture resembles fine crumbs before adding the egg and 2 tbsp iced water, adding more if needed.) Turn out onto a lightly floured work surface and knead until smooth. Wrap and chill in the fridge for 30 minutes to rest.
2. Meanwhile, heat the oven to 200°C/180°C fan/gas 6 and put a baking sheet in the oven. Heat the oil in a large frying pan over a medium heat. Working in batches, fry the chicken for 2-3 minutes on each side until browned and cooked through. Remove from the pan and set aside.
3. Wipe the pan clean, then return to a medium heat. Add the butter, garlic and leeks and cook for 8-10 minutes until starting to soften. Stir in the flour, then gradually add the stock, whisking continuously to stop lumps forming. When you have added all the stock and the mixture has thickened (about 4-5 minutes), stir in the cream and both mustards, followed by the chicken and ham. Season lightly with salt and pepper, then set aside to cool (see tips).
4. While the mixture is cooling, roll out two thirds of the pastry on a lightly floured surface to 3mm thick and large enough to line the base and sides of your pie dish. Line the pie dish with the pastry, then trim off any excess and reserve to decorate the pie. Pour in the cooled chicken mixture.
5. Roll out the remaining pastry to a 30cm x 24cm rectangle, then cut into 15 strips (2cm x 24cm).
6. Brush the edge of the pie with beaten egg, then top with the strips, interlacing them to create a lattice pattern (see our how-to video).
7. Trim the lattice ends, then press to seal the edges and brush the lattice with beaten egg. Roll out any pastry trimmings and cut into shapes for extra decoration, using biscuit cutters if you like. Add to the pie top and brush with more beaten egg (see Make Ahead).
8. Put the pie in the oven on the heated baking sheet and cook for 35-40 minutes until golden. Leave to stand for 10 minutes before slicing and serve with steamed new potatoes and green beans.