The Ultimate Cheesy Smoked Brisket Pie

Sauté Aromatics: Heat the olive oil or butter in a large saucepan or pot over medium heat. Add the diced onion and sauté for about 5-7 minutes until soft and translucent. Add the minced garlic and cook for 1 minute more until fragrant.
Thicken the Base: Sprinkle the flour over the onions and garlic, stirring constantly for 1-2 minutes. This creates a roux to prevent lumps and deepen the flavor.
Build the Gravy: Gradually whisk in the beef stock until the mixture is smooth. Bring the mixture to a low simmer, stirring occasionally until the gravy begins to thicken (about 5 minutes).
Add Brisket and Seasoning: Stir in the shredded smoked brisket, BBQ sauce (if using), and mixed herbs. Season with salt and black pepper to taste. Cook for another 5 minutes, ensuring the brisket is well-coated and heated through.
Cool Down: Remove the filling from the heat and set it aside to cool completely. Cooling is crucial to prevent the puff pastry from becoming soggy.

Preheat Oven: Preheat your oven to $200^\circ\text{C}$ ( $400^\circ\text{F}$ ).
Prepare the Dish: Lightly grease a deep-dish pie plate or an oven-safe baking dish (around 8-9 inches).
Line the Base (Optional): If using a bottom crust, carefully line the base and sides of your dish with one sheet of puff pastry. Trim the edges.
Fill the Pie: Spoon the cooled brisket filling into the prepared pie dish.
Add the Cheese Layer: Generously sprinkle the shredded cheese blend over the top of the brisket filling. This will create the gooey, melted layer seen in the photo.

Create the Lid: Lay the second sheet of puff pastry over the filling. Trim the edges and crimp the dough to seal the top and bottom crusts (if using a bottom crust) or simply seal it to the rim of the dish.
Vent: Cut a few slits in the top pastry (the ‘vent’) to allow steam to escape during baking.
Egg Wash: Brush the entire surface of the top pastry with the beaten egg wash. This gives the pie its signature golden, glossy finish.
Bake: Bake for 25-30 minutes, or until the puff pastry is beautifully golden brown, flaky, and the filling is piping hot and bubbling from the vents.
Rest: Allow the pie to rest for 10-15 minutes before slicing and serving. This helps the filling set and makes for cleaner cuts.