• Preheat oven to 180C.

For the pie shortcrust

• Place flour and butter in a food processor and blitz until it resembles breadcrumbs. Add egg yolk, a pinch of salt and enough water just to bring dough together (about 11/2 tbsp). Pulse until mixture comes together. Turn out onto bench, form into a round, wrap in plastic wrap and rest for 30 minutes.

For the pie filling

• Place butter and olive oil in a large pan over medium heat. Add leek and cook until softened, about 2 minutes.
• Add bacon and continue cooking for a further 5 minutes.
• Add chicken and thyme and continue cooking until chicken is just cooked through, about another 5 minutes.
• Add flour to pan and cook, stirring, for 1 minute. Add chicken stock and 375ml water and bring to a simmer, stirring continuously until sauce has thickened.
• Stir through lemon juice and zest and season. Set aside to cool.
• Roll dough out on a clean, lined bench to 2mm thickness and cut 6 circles of pastry to fit 7.5cm base pie tins. Spoon filling into cases and cover with another layer of pastry.
• Crimp the edges of the pie and place in the oven to bake until pastry is golden and crisp and filling is cooked through, about 20-25 minutes.