Prepare the Filling

1. Sauté Vegetables: In a large skillet, heat olive oil over medium heat. Add the onions, garlic, carrots, and celery. Sauté until vegetables are tender, about 5 minutes.
2. Add Mushrooms: Stir in mushrooms and cook until they release their moisture, around 3 minutes.
3. Combine Brisket and Liquid: Add the shredded brisket, beef broth, red wine (if using), and Worcestershire sauce. Stir to combine.
4. Thicken the Mixture: Sprinkle flour over the mixture and stir until thickened. Season with salt and pepper to taste.
5. Add Peas: Stir in frozen peas and let the filling cool slightly.

Assemble the Pot Pie

1. Preheat Oven: Preheat oven to 375°F (190°C).
2. Fill the Pie: Pour the brisket mixture into a pie dish or baking dish.
3. Top with Crust: Lay the pie crust over the filling, trimming any excess and crimping the edges. Cut a few small slits on top to allow steam to escape.
4. Brush with Egg Wash: Brush the top of the crust with beaten egg for a golden finish.

Bake

1. Bake: Place in the oven and bake for 30-35 minutes, or until the crust is golden brown and the filling is bubbling.
2. Cool: Allow the pot pie to cool for 10 minutes before serving.