Chicken and bacon pie recipe

Ingredients

• 1 kg skinless, boneless chicken thighs, chopped into bite-size pieces
• 8 rashers of dry-cured, smoked streaky bacon, cut into bite-size pieces
• 1 tbsp mild olive oil
• 2 onions, finely sliced
• 2 stalks of celery, finely sliced
• 3 medium leeks, finely sliced
• 4 fresh thyme sprigs, leaves picked
• 1 tbsp butter
• 200 g button mushrooms
• 2 tbsp plain flour, plus extra for rolling
• 400 ml chicken stock
• 200 ml crème fraîche or double (heavy) cream
• 1 tsp Dijon mustard
• 500 g frozen puff pastry or ready-to-roll pie crust, defrosted
• 1 medium egg
• 1 pinch salt and pepper