How to make Pieminister's chicken, cider and leek pie for British Pie Week

How to make Pieminister’s ‘The Free Ranger’ pie

1 free-range British chicken, about 1.5kg
1 carrot, peeled and cut into quarters
2 celery sticks, cut into quarters
2 onions, cut in half
1 whole bulb of garlic, top sliced off
6 sprigs of tarragon
1 large knob of butter
3 chunky leeks, cut in half lengthwise, then sliced
200ml dry or medium cider, preferably Orchard Pig
2 tbsp plain flour
150ml single or whipping cream
Grated zest of ½ lemon
3 tbsp chopped chives
1 quantity of shortcrust pastry for the base (you can find a recipe on page 10 of Pieminister’s cookbook ‘A Pie for All Seasons’) or cheat with 660g of ready-made shortcrust pastry
1 free-range egg, lightly beaten, to glaze
1 quantity of rough puff pastry for the top (you can find a recipe on page 10 of Pieminister’s cookbook ‘A Pie for All Seasons’) or cheat with 375g ready-made puff pastry
Sea salt and black pepper