Preheat oven to 375 degrees F (190 degrees Celsius).
On a lightly floured surface, carefully roll out one of the pie crusts. Transfer the pie crust to a prepared pie pan that has been sprayed with non-stick spray.
**Note - To help with the transfer of the dough, roll the dough loosely onto the rolling pin and unroll it carefully over the pie pan. Press the dough into the pie pan and allow the excess to fold over the sides of the pan. Set aside.
Melt the butter In a 3 quart saucepan over medium heat. Add the flour and cook for 2-3 minutes, stirring occasionally. Switch to a whisk and add the chicken stock, salt, pepper, garlic, and Dijon mustard. Whisk continually until the mixture heats and thickens (approximately 4-5 minutes).
Using a wooden spoon, stir in the thyme, mustard, pork, minced garlic, and frozen vegetables. Cook, stirring occasionally to heat through.
Carefully pour the pork filling into the prepared pie crust. On a lightly floured surface, roll the second pie crust out like the first one. Transfer the dough over the pork filling (on the rolling pin) and carefully unroll to cover.
Use a paring knife to trim the excess dough away (saving some for the leaf garnish, optional), and use a fork to press and seal the bottom and top crusts together.
Use a paring knife to cut steam holes into the top crust, and insert a pie bird (optional).
Use some of the trimmed dough to cut out leaf shapes and use a little water to adhere the leaves to the top of the pie (optional).
In a small bowl, whisk the egg and 1 tablespoon water. Brush the egg wash over the top crust.
Place the pie on a baking sheet and bake in a preheated oven for 40-45 minutes or until the crust is golden brown and the filling is heated through.
Cool for at least 20 minutes and serve.
Notes
Store any leftovers in an airtight container in the refrigerator for up to 5 days.Pork Pot Pie may be frozen after baking. Cool completely and store the entire pie, or individual servings in airtight freezer containers or bags and freeze for 2 months.Thaw in the refrigerator overnight and heat, uncovered, in a preheated 350 degree F oven (175 degree C) until hot.