Preheat the oven to 400°F (200°C).
In a large skillet, sauté the diced onions over medium heat until translucent.
Add the shredded chicken and frozen vegetables to the skillet, cooking for about 5 minutes.
Sprinkle the flour over the mixture and stir well to combine.
Slowly add the chicken broth and heavy cream, stirring continuously until the mixture is smooth.
Season with garlic powder, thyme, salt, and pepper, adjusting to taste.
Remove the skillet from heat and let the filling cool slightly.
Roll out the pie crusts and cut into circles to fit your muffin tin.
Place the crusts in a greased muffin tin and fill each with the chicken mixture.
Top each pie with an additional circle of crust, sealing the edges and slitting the tops for steam.
Brush the tops with the beaten egg for a golden finish.
Bake in the preheated oven for 20-25 minutes or until the crust is golden brown.
Let the mini pot pies cool for a few minutes before serving.
