1.In a pan, melt the butter on medium heat.
2.Add onion, carrot, and celery and saute for 5 to 6 minutes or until translucent.
3.Add mushrooms and cook for 5 to 6 minutes.
4.Now add flour to the pan and cook for 2 to 3 minutes.
5.Remove the pan from heat, add chicken stock gradually, and stir to avoid any lumps.
6.Cook the mixture for 2 to 3 minutes while stirring. Add heavy cream and stir to combine , creating a thick gravy-like mixture.
7.Add Italian herb seasoning, salt, and pepper. Taste to adjust the seasoning.
8.Add chicken and frozen peas to the mixture and mix. Set aside to cool to room temperature.
9.Preheat the oven to 400 F.
10.Place one pie crust in a pie pan and gently press it to cover the edges of the pan.
11.Pour the chicken filling and cover the pan with a second pie crust.
12.Cut the excess crust and cramp the edges to seal with a knife. Then, cut an X in the middle for air to escape.
13.Brush the top with egg.
14.Bake the pot pie for 20 to 25 minutes or until golden.
15.Let it rest for 15 minutes, and then serve.