Start by preparing your homemade pie crust. Roll it out to fit your pie dish, ensuring it’s about 1/8 inch thick. Place it in the dish and trim any excess. If you're in a hurry, store-bought crusts work too!
In a large skillet, melt the 6 tablespoons of unsalted butter over medium heat. Add the chopped yellow onion and sauté for about 3-4 minutes until translucent. Then, add the carrots and mushrooms, cooking until they're tender, about 5-7 minutes. Finally, stir in the minced garlic and cook for an additional minute.
Sprinkle the flour over the vegetable mixture and stir to combine. Cook for about 1-2 minutes to eliminate the raw flour taste. Gradually add the chicken stock while whisking continuously to avoid lumps, followed by the heavy cream. Bring the mixture to a gentle simmer and cook until thickened, about 5-7 minutes. Stir in the shredded chicken, frozen peas, parsley, salt, and black pepper. Remove from heat.
Pour the filling into the prepared pie crust. Roll out the second pie crust to cover the filling, placing it on top. Trim any excess and crimp the edges to seal. Cut a few slits in the top crust to allow steam to escape.
Preheat your oven to 425°F (220°C). Brush the top crust with the beaten egg for a beautiful golden finish. Bake for 30-35 minutes or until the crust is golden brown and the filling is bubbly. If the edges brown too quickly, cover them with foil.
Allow the Chicken Pot Pie to cool for about 10-15 minutes before serving. This will help the filling set slightly and make it easier to slice.
