In a large skillet, melt 4 tablespoons of unsalted butter over medium heat. Once bubbly, add 1 chopped onion and sauté until soft and translucent, about 5 minutes. Stir in 2 minced garlic cloves and cook for an additional 30 seconds until fragrant.

Sprinkle 1/3 cup of all-purpose flour into the skillet and stir constantly for 2-3 minutes until it turns light golden brown.

Slowly whisk in 2 cups of chicken broth and 1 cup of milk or cream, cooking until the sauce thickens and becomes smooth, about 5-7 minutes.

Once thickened, season with salt, pepper, and 1 tablespoon of fresh parsley. Fold in 2 cups of cooked chicken chunks and 2 cups of mixed vegetables until well-combined.

Remove from heat and cool for 10-15 minutes. Preheat your oven to 425°F (220°C).

Roll out one pie crust and place it in the bottom of a 9-inch pie pan, then pour the cooled filling into the crust. Lay the second pie crust on top, crimp edges to seal, and cut slits for steam.

Brush the top crust with a beaten egg for a golden finish. Bake for 30-35 minutes, until the crust is golden brown and filling is bubbling.

Let it rest for 15 minutes before slicing.