01 - Preheat your oven to 400°F (200°C) to ensure it's ready for baking.
02 - In a large skillet set over medium heat, melt the unsalted butter. Add the diced onion, carrots, and celery, and sauté for 5–7 minutes until they begin to soften. Incorporate the minced garlic and cook for an additional minute until fragrant.
03 - Sprinkle the all-purpose flour evenly over the sautéed vegetables. Stir continuously and cook for 2 minutes, allowing the flour to toast slightly and form a roux, which will serve as a thickener for the sauce.
04 - Gradually whisk in the low-sodium chicken broth, whole milk, and heavy cream until the mixture is smooth and lump-free. Bring it to a gentle simmer, stirring constantly, until it thickens to a desired consistency, typically within 3–5 minutes.
05 - Stir in the diced cooked turkey, frozen peas, salt, black pepper, dried thyme, and dried sage. Allow the mixture to simmer for 2 minutes to meld the flavors thoroughly. Remove the skillet from the heat.
06 - Spoon the prepared pot pie filling evenly into a 9-inch deep-dish pie plate or a similar oven-safe baking dish, ensuring the ingredients are well distributed.
07 - Roll out the thawed puff pastry sheet to a size that adequately covers your baking dish. Carefully place it over the filling, pressing the edges firmly against the rim of the dish to create a secure seal. Cut several small slits on top of the pastry to allow steam to escape during baking.
08 - Brush the top surface of the puff pastry generously with the beaten egg. This egg wash will help achieve a beautiful golden-brown and glossy finish during baking.
09 - Transfer the prepared pot pie to the preheated oven and bake for 25–30 minutes, or until the puff pastry is beautifully golden brown and the filling is visibly bubbling around the edges.
10 - Remove the pot pie from the oven and allow it to rest for 10 minutes before serving. This resting period allows the filling to set properly, preventing it from being too runny, and ensures safer handling.