• Preheat oven to 425 degrees.
• In a 12" saute pan over medium heat, add 2 tablespoons of butter. When hot, add cubed chicken. Cook for 3-4 minutes, stirring occasionally, until cooked through. Remove from pan, set aside, and cover to keep warm.
• Add remaining 2 tablespoons of butter, onions, and celery. Cook for 4-5 minutes or until vegetables begin to brown. Add garlic and cook an additional 30 seconds.
• Add flour to pan and stir to coat vegetables. Cook for 1 minute, then add chicken broth and milk. Whisk to incorporate, scraping the bottom of the pan as needed. Add thyme, salt, pepper, and peas & carrots. Stir to combine.
• Bring to a simmer, and allow sauce to cook until thickened slightly, up to 5 minutes. Once sauce has thickened, remove from heat, add chicken, and stir to combine.

Biscuits

• In a large bowl, combine flour, baking powder, baking soda, and salt. Whisk to combine and remove clumps.
• Grate butter (or cut into small pieces). Add butter to flour mixture, stirring to combine. Make a well in the center of the flour mixture. Add buttermilk and stir until barely incorporated. 
• Toss dough out onto a lightly floured surface. Handling as little as possible, fold dough in half five times, then pat to a 1 inch thickness. 
• Using a biscuit cutter, cut out biscuits and place on top of your pot pie filling.
• Bake entire dish for 16-18 minutes, or until biscuits are browned on top.