1-First Step: Mise en Place: Dice 2 cups cooked chicken into bite-sized pieces. Slice 1 cup carrots and celery thinly for even cooking. Measure 1 cup peas, dice 1 onion, and gather all other ingredients. Preheat oven to 425°F. Grease a 9-inch pie dish. This setup keeps cooking smooth and stress-free.

2-Second Step: Cook the Vegetables: Heat a large skillet over medium heat. Add 1 tablespoon butter or oil, then saute diced onion until soft, about 3 minutes. Stir in sliced carrots and celery. Cook until tender-crisp, 5 minutes. Add peas and cook 2 more minutes. Remove veggies to a bowl, keeping juices for flavor.

3-Third Step: Make the Creamy Sauce: In the same skillet, melt 1/4 cup butter over medium heat. Whisk in 1/4 cup flour to form a smooth roux; cook 1-2 minutes to remove raw taste. Slowly pour in 2 cups chicken broth while whisking constantly to avoid lumps. Add 1/2 cup milk. Simmer until thickened, 5-7 minutes. Season with salt, pepper, 1 teaspoon thyme, and 1/2 teaspoon onion powder. Taste and adjust.

4-Fourth Step: Combine Filling: Stir cooked chicken and vegetables into the sauce. Mix well to coat everything evenly. Simmer 2 minutes for flavors to meld. If too thick, add a splash of broth. Pour mixture into prepared 9-inch pie dish. Smooth top for even baking.

5-Fifth Step: Add the Crust: Unroll unbaked pie crust over filling. Trim excess, crimp edges to seal. Cut 3-4 vents in center for steam escape. Brush with beaten egg wash for golden shine. For puff pastry version, thaw sheet, place atop, trim, score lightly.

6-Sixth Step: Bake to Perfection: Bake at 425°F for 30-35 minutes until crust turns deep golden and filling bubbles. For puff pastry at 400°F, 25-30 minutes. If edges brown too fast, tent with foil. Rest 10 minutes post-bake; filling sets for clean slices.

7-Final Step: Serve and Enjoy: Slice into 6 portions. Pair with green salad or rolls for potluck. Leftovers reheat beautifully. This easy chicken pot pie with puff pastry option suits quick nights too.