A moreish pie with a crumble topping from Diana Henry.
Remove the discoloured outer leaves from the leeks and trim the tops and bases. Cut into 1.5 cm lengths and wash thoroughly.
Melt 15g butter in a heavy-bottomed saucepan and cook the leeks over a medium heat for about 5 minutes. They shouldn’t colour.
Add a couple of tablespoons of the cider and cover the pan. Cook on a low heat for 5-7 minutes until the leeks are soft but retain their shape.
Melt the rest of the butter in a saucepan and stir in the flour. Cook over a medium heat for about a minute to form a roux.
Take the pan off the heat and add the milk a little at a time, stirring well after each addition to keep the mixture smooth. After all the milk has been added, stir in the rest of the cider. Put the saucepan back on the heat and bring to the boil, stirring all the time, to form a thick sauce.
Once it starts to boil, turn down to a simmer for 3 minutes to 'cook out’ the flour.
Season, then stir in the mustard, the leeks and their cooking juices, and chicken. Heat through thoroughly, add the cream if you’re using it (it brings a touch of luxury but isn’t necessary) and taste for seasoning. Pour the mixture into an ovenproof pie dish or pan.
Preheat the oven to 190C/170C Fan/Gas 5. For the crumble, put the flour, breadcrumbs and butter into a bowl and rub the mixture between your fingers until little lumps form. Add the rest of the ingredients. Spread over the chicken and leek mixture and bake for 30 minutes, until golden brown.