In a food processor, combine 450g of plain flour and 225g of cold, diced salted butter. Pulse until the mixture resembles pea-sized crumbs. Add one large egg and then gradually pour in ⅔ cup of very cold water. Pulse until the dough starts to clump together. Wrap in plastic, refrigerate for at least 1 hour to let it chill and firm up.

In a large skillet over medium-high heat, warm 1 tablespoon of vegetable oil. Add 250g of diced bacon and cook until golden and crispy, about 5-7 minutes. Then, add 700g of diced boneless, skinless chicken thighs and cook until evenly browned, approximately 6-8 minutes, stirring occasionally. Remove from heat, set aside, and deglaze the pan with a splash of water to loosen any flavorful bits.

In the same skillet, toss in 1 diced medium brown onion, 2 finely diced medium carrots, and 2 finely diced celery sticks. Stir in 2 teaspoons of fresh thyme leaves for extra flavor. Sauté the mixture over medium heat for about 5 minutes until the vegetables are softened and fragrant.

To the softened vegetables, stir in ⅓ cup of apple cider, scrapping up any remaining bits from the pan. Next, sprinkle in 2 tablespoons of flour, stirring continuously for about a minute before adding 1 ¾ cups of chicken stock and ½ cup of thickened cream. Mix in 1 tablespoon of Dijon mustard, then let the gravy simmer for around 5-10 minutes until it thickens, stirring occasionally. Fold in the cooked bacon and chicken, then allow to cool.

Preheat your oven to 200°C (400°F). On a floured surface, roll out half of your chilled pie crust to fit a pie dish. Carefully line the bottom of the dish with the rolled crust. Spoon the cooled chicken and bacon filling into the crust, spreading it evenly. Roll out the second half of the crust to cover the filling, crimping the edges to seal, and create vents for steam.

Brush the top crust with a beaten egg to achieve a golden finish. Place the Chicken and Bacon Pie into the preheated oven and bake for 50-60 minutes, or until the crust is golden brown and crisp. Once done, let it rest for about 10 minutes before slicing and serving.