For the Crust:

Preheat your oven to 425°F (220°C).

In a medium mixing bowl, combine the gluten-free flour, salt, and xanthan gum.

With a pastry knife, cut the cold butter into the flour until the pieces are the size of small peas.

Add the cold milk, and mix until combined. You may need to use your hands to work the milk into a moist, rollable dough.

Divide the dough in half and roll each ball on a gluten-free floured surface until approximately 10 inches in diameter.

Place one circle of dough into a pie pan and trim the edges if necessary.

For the Filling:

Combine chicken, carrots, and peas in a medium saucepan. Cover with water and boil for 15 minutes. Drain and set aside. (If using precooked chicken, just cook the peas and carrots, then add the chicken after draining).

In the same saucepan over medium heat, cook onions in butter until soft and translucent.

Stir in the gluten-free flour, salt, and pepper.

Slowly stir in the chicken broth and milk. Simmer over medium-low heat until thick, then remove from heat.

Place the chicken and veggie mixture in the bottom crust, filling it about halfway. Pour the gravy mixture over the top, filling it about 3/4 full.

Assembly and Baking:

Cover with the top crust, seal the edges, and cut away excess dough.

Cut small slits into the top to let steam escape.

Bake for 30 to 35 minutes, or until the pastry is golden brown and the filling is bubbling.

Allow it to cool for 15 minutes before serving.