Make Crust

1. Add the flour, salt, and baking soda to your food processor. Pulse a few times to combine
2. Add pieces of cold butter to the mixture and pulse again until butter is in pea-sized pieces
3. Add the ice water and pulse again until you can see it start to come together. This will probably take between 30-40 pulses. If it still seems too dry, add 1-2 tbsp extra ice water
4. Turn the dough onto a floured surface and form 2 equal round discs. Wrap them separately and refrigerate for at least 1 hour, or up to 1 day. When ready to use, rest at room temperature 10 minutes before rolling. Meanwhile, prepare filling

Prepare Filling

1. In a medium saucepan, add the butter and melt over low heat. Whisk in the flour to create a roux to help thicken the sauce. Cook 2-3 minutes, whisking to prevent lumps
2. Add the chicken stock and a pinch of salt and pepper. Whisk together well. Raise heat to medium. Allow liquid to cook and thicken, 5-10 minutes. Once thick, add the vegetables and chicken. Mix well to assure that everything is evenly covered in the sauce. Season with salt and pepper

Assemble & Bake

1. Preheat oven to 400º
2. Roll both dough disks into ¼”-thick rounds on a floured board
3. Lay 1 piece of rolled dough on bottom of a 9” pie plate, allowing dough to extend over sides of plate
4. Spoon filling into pie plate and smooth out to accommodate top crust; fill no more than ⅔ of the way up the crust to avoid spillover in the oven
5. Top with second piece of rolled dough. Crimp top and bottom pieces of dough together using fingers to pinch and form along edge. Ignore excess dough until the whole pie has been crimped. Take a paring knife and run it along outside of plate to remove excess dough. [Note: save the scraps to roll, cut & bake with cheese or cinnamon & sugar!]
6. Cut slits in top crust (4-6 slits, about 1") to allow steam to escape while cooking
7. Bake 45 minutes, or until crust is golden brown
8. Cool 15-20 minutes before slicing and serving