Step 1

Melt butter in a saucepan over low heat until foaming. Add leek and cook, stirring, for 5 minutes or until the leek softens. Add flour and cook, stirring, for 5 minutes or until mixture bubbles. Remove from heat. Gradually add stock, whisking until smooth.

Step 2

Whisk the cream, tarragon and pepper into the flour mixture. Season with salt. Stir in the chicken. Set aside to cool completely.

Step 3

Preheat oven to 200°C. Position an oven rack on the lowest shelf of oven. Place the extra flour and salt in the bowl of a food processor.

Step 4

Place the unsalted butter, milk and water in a saucepan over low heat. Cook, stirring, for 2 minutes or until the butter melts. With the motor running, gradually add the butter mixture to the flour mixture in the food processor until the dough just starts to come together. Turn onto a lightly floured surface and knead until just smooth.

Step 5

Divide the pastry into 3 portions. Roll out 1 portion until 4mm thick. Line a 22cm (base measurement) springform pan with the pastry, allowing side to overhang. Spoon the chicken mixture into the pan.

Step 6

Roll out the remaining pastry until 4mm thick. Place over chicken mixture and trim edge to fit. Fold over the side to enclose the filling. Cut 3 small slits in the centre of the pie to allow steam to escape. Use a knife to cut leaves from excess pastry to decorate the pie. Brush pie with egg. Bake on lowest shelf of oven for 35 minutes or until crisp and golden. Set aside to cool slightly. Serve cold or warm.