Step 1: Prepare the Chicken and Leek Filling
- Heat the Oil: In a large frying pan, heat the olive oil over medium heat.
- Cook the Chicken: Add the chicken pieces to the pan and cook until browned on all sides. Remove the chicken from the pan and set aside.
- Sauté the Vegetables: In the same pan, add the chopped onion, garlic, and sliced leeks. Cook for about 5 minutes until the vegetables are softened.
- Thicken the Sauce: Sprinkle the flour over the vegetables and stir to coat. Cook for 1-2 minutes to eliminate the raw flour taste.
- Add Stock and Cream: Gradually pour in the chicken stock, stirring continuously to prevent lumps. Add the double cream and Dijon mustard, and stir until the sauce is smooth and thickened.
- Combine with Chicken: Return the browned chicken to the pan, stir to combine, and cook for another 5 minutes until the filling is heated through. Season with salt, pepper, and thyme leaves if using. Remove from heat and let the filling cool slightly.
Step 2: Prepare the Pastry
- Roll Out the Pastry: On a lightly floured surface, roll out the pastry to fit the top of your pie dish, with a little extra to hang over the edges.
- Line the Pie Dish (Optional): If you prefer a pastry base, line the pie dish with a portion of the rolled-out pastry, trimming any excess.
Step 3: Assemble the Pie
- Preheat the Oven: Preheat your oven to 200°C (400°F).
- Fill the Pie Dish: Spoon the chicken and leek filling into the prepared pie dish, spreading it evenly.
- Cover with Pastry: Place the rolled-out pastry over the top of the filling, pressing down around the edges to seal. Trim any excess pastry and crimp the edges with a fork or your fingers.
- Glaze the Pastry: Brush the top of the pastry with the beaten egg to give it a golden finish.
- Cut a Steam Hole: Make a small cut in the center of the pastry to allow steam to escape during baking.
Step 4: Bake the Pie
- Bake Until Golden: Place the pie on a baking tray to catch any drips, and bake for 25-30 minutes, or until the pastry is golden brown and crisp.
- Cool Slightly: Allow the pie to cool for a few minutes before serving.