Preheat oven to 400˚F. Melt butter in a medium saucepan over medium-high heat. Add onions, carrot and celery and sauté for 3 to 4 minutes. Add thyme and season with salt and pepper.
Reduce heat to medium and stir in flour and cook for 2 minutes.
Stir in stock, followed by milk and continue to stir until mixture thickens enough to coat the back of a wooden spoon, 3 to 4 minutes.
Fold in chicken and peas. Adjust seasonings as needed.
Assembly
Place each skillet onto a baking sheet. Scoop chicken mixture into individual skillets
Top each skillet with a square of puff pastry.
Brush each square of puff pastry with egg wash.
Bake for 15 to 20 minutes or until puff pastry has puffed and browned. Remove from oven, cool slightly and serve.
Notes
Tips and Tricks
To save time, you can pre-chop your carrots, onions, and celery and store them in an airtight container in the refrigerator for up to 3 days before making your chicken pot pie.
Be careful not to burn the flour when adding it to the vegetables, but cook long enough so that the flour is actually cooked. Stir frequently and wait for a slightly nutty aroma.
Add the stock into the pot slowly, stirring as you do to avoid clumps. Using a whisk can help all of the stock and flour incorporate smoothly into the flour and vegetable mixture.
You can use either cooked chicken breast or chicken thighs or, to save even more time, shredded and chopped rotisserie chicken!
Make AheadYou can easily make this dish ahead of time and assemble and bake it when you're ready to eat. Prepare the filling as directed, then let it cool and store in the refrigerator for up to two days. When you're ready to make your pot pie, follow the assembly directions and bake!StoringTo store leftovers, let the chicken pot pie cool, then cover and store in the refrigerator for 3-4 days. To reheat, preheat the oven to 350˚F and bake your pot pie for 15-20 minutes or until heated through. If the top begins to brown too much, cover it in foil.FreezingYou can easily prepare your pot pie ahead of time and freeze it to be cooked at a later date.For a pot pie that you can remove from the freezer and bake: make the filling and let it fully cool. Add it to an oven and freezer-safe pan or pie dish. Top with puff pastry and then freeze it for 2-3 hours. Once the puff pastry has been somewhat frozen, wrap the dish in plastic wrap, then foil (pre-freezing the dish keeps the plastic from sticking to the puff pastry). Freeze for up to 3 months. To bake, remove from the freezer and remove the plastic wrap. Add an egg wash to the top of the puff pastry, then bake as directed. You may need to add an additional 15-20 minutes of baking time (and possibly cover the top in foil if it starts to brown to quickly).