Prepare 2 pie crusts by doubling my gluten-free pie crust recipe, including chilling.
Place a baking sheet on the lower rack of the oven. Preheat the oven to 425°F and grease a 9-inch pie dish with gluten-free cooking oil cooking spray.
Place one of the gluten-free pie doughs into the bottom of the greased pie dish. Make sure it is smooth.
Place the diced potatoes and frozen vegetables in a large pot. Cover the vegetables with the 1 cup water to cover and cook over medium heat for 10-15 minutes, until potatoes are soft. Drain the vegetables and place in a bowl.
Add the butter to the pot and melt over medium heat. In a small bowl whisk together the milk and gluten-free flour. Stir in gluten-free flour and seasonings, whisking continuously until smooth.
Add the gluten-free chicken broth, stirring frequently until thick. Remove the pot from heat.
Stir in the chopped chicken and vegetables. Pour the filling into the pie crust.
Place the remaining pie crust over the top of the filling and pinch the edges shut. Cut slits in the top of the pot pie.
Whisk together the egg and the water in a small bowl and brush it all over the top crust.
Bake for 30-35 minutes, or until golden brown and internal temperature reaches 165°F.
Allow the pot pie to cool for 10 minutes and serve!
