Hot-water crust chicken, leek and shiitake pie

INGREDIENTS

medium leek, trimmed and sliced into thin rings

120 g

shiitake mushrooms, stalks discarded, caps finely sliced

25 g

butter

400 g

cold cooked chicken, shredded

1 tbsp

chopped tarragon

1 tbsp

chopped parsley

40 g

butter

40 g

flour

300 g

fresh chicken stock

150 milliliters

single cream

1 tsp

English mustard

good squeeze of lemon

175 g

plain flour, sifted, plus a little extra for dusting

50 milliliters

milk

10 g

butter

large egg, lightly beaten

25 x 18cm (1.5-litre) pie dish or similar