2. Stir the chicken and tarragon into the sauce, then spoon the mixture into a 23cm round pie dish. 3. Top with the pastry, pressing it along the edge of the dish to seal and trimming off any excess.

To assemble the pie: Drop the chicken into the leek and the mushroom sauce, add the parsley, season and stir it all together. Spoon the pie filling into a lasagne dish and leave the mixture to ...