1. Make the Crust: Preheat oven to 425°F (220°C). In a medium bowl, combine flour, salt, and xanthan gum. Cut the cold butter into the flour with a pastry knife until it resembles small peas.

2. Form Dough: Add cold milk and combine until a moist dough forms. You may need to use your hands. Divide dough in half.

3. Roll Dough: On a gluten-free floured surface, roll each dough half into a 10-inch circle. Place one circle into a pie pan for the bottom crust.

4. Cook Filling Base: In a saucepan, combine chicken, carrots, and peas. Cover with water, boil for 15 minutes, then drain and set aside.

5. Make Gravy: In the same pan, melt ⅓ cup butter and cook onions until soft. Stir in flour, salt, and pepper. Slowly whisk in chicken broth and milk.

6. Thicken and Assemble: Simmer the gravy over medium-low heat until thick. Place the chicken/veggie mixture into the bottom pie crust. Pour the gravy over the top.

7. Top and Bake: Cover with the top crust, seal the edges, and cut slits in the top. Bake for 30 to 35 minutes, until the pastry is golden brown and the filling is bubbly.

8. Rest: Cool for at least 15 minutes before serving to allow the filling to set.