Creamy filling, flaky puff pastry top, steam rising as you crack through the crust. Chicken pot pie is the Sunday high calorie dinner that feels like home.
Preheat your oven to 400°F (200°C) with the rack in the center. Lightly grease a deep pie dish or casserole.
In a large skillet over medium-high heat, melt the unsalted butter until foamy. Add diced onions, carrots, celery, and potato; sauté 5–6 minutes until just tender, stirring to avoid browning.
Add garlic and fresh thyme, cook 1 minute. Sprinkle in all-purpose flour and stir constantly for 2 minutes to form a roux, adjusting heat to medium if needed to avoid burning.
Slowly whisk in chicken broth and whole milk, scraping up any flour bits from the pan. Continue stirring until mixture thickens and bubbles, about 5–7 minutes, then season with salt and black pepper.
Add chicken thighs (cut into bite-size pieces). Simmer gently for 10 minutes until just cooked through, stirring occasionally. Add peas in the last 2 minutes. Remove from heat.
Pour the filling into your prepared pie dish. Roll out puff pastry sheets to fit over the dish and drape them carefully over the filling. Press edges to seal and trim excess; cut a few small slits in the top for steam to escape.
Beat egg and brush over the pastry for a shiny, golden finish. Place the dish on a baking sheet to catch drips and bake for 25–30 minutes, or until the pastry is deeply golden and puffed.
Let the pot pie rest 10 minutes after baking for the filling to set slightly. Serve hot, making sure to break through the pastry to release the aromatic steam.