Instructions

1. In a large skillet or Dutch oven, melt 6 tablespoons of butter. Add diced onions, carrots and celery and saute about 10 minutes over medium heat until veggies are starting to get soft.
2. Push the mixture to the side of the pan, turn up the heat a bit and add the mushrooms, as much as possible in a single layer. Allow them to cook on one side until  browned. Then mix all the veggies together and add the garlic. Stir and saute for another minute or two.
3. Add the flour and stir for a minute or two. Add the salt, pepper and thyme and continue to stir and cook, stirring constantly, for another minute.
4. Add chicken stock and milk. Bring the mixture to a simmer and cook for a few minutes until it thickens.
5. Add chicken, peas, and parsley. Stir and cook for a couple minutes. Taste and add more salt and pepper if desired. Remove from heat and set aside to cool slightly.
6. While the chicken and vegetable mixture is cooling, roll out half your pastry dough into an 12 inch circle and place it into your pie pan. Pour the chicken and vegetable mixture over the crust.
7. Roll out the other half of the pie dough into a 10 inch circle and place over the filling. Fold the edges of the pie dough over and crimp to seal and form a nice edge.
8. With a sharp paring knife, poke 8 to 10 slits in the top of the pastry. Whisk together the egg and 1 tablespoon of milk, and brush this mixture over the top of the pie. Sprinkle lightly with kosher salt.
9. Bake at 425 degrees for 30 to 40 minutes or until the top crust is golden brown and the filling is bubbling through the slits in the pie crust. Allow the pie to cool on a rack for 10 to 20 minutes before serving.