Chicken Pot Pie with Puff Pastry

Preheat the oven to 400°F (200°C).

Roll out one sheet of puff pastry into an 11-inch square. Fit it into a 9-inch pie dish, trim off excess pastry, and poke holes all over with a fork. Cover the pastry with aluminum foil.

Bake the pastry in the preheated oven until it's puffed up and golden brown, about 25 minutes. Remove from the oven, discard the foil, and set aside.

While the pastry is baking, melt butter in a skillet over medium-low heat. Add onions and celery, cooking until tender and translucent, about 5 minutes. Stir in the flour, salt, pepper, and celery seed, and cook until the mixture thickens into a paste.

Gradually pour in the milk while stirring constantly, about 5 minutes. Continue to stir as you slowly add the broth in small amounts. Cook the mixture until it thickens, about 7 to 10 minutes. Stir in the chicken and frozen vegetables, cooking until the vegetables are thawed, about 3 to 5 minutes.

Transfer the chicken mixture into the pre-baked puff pastry shell. Roll out the second sheet of puff pastry into an 11-inch square and place it over the chicken filling. Trim off any excess pastry and press the edges together to seal.

Bake the pie in the preheated oven until the top pastry is golden brown, 45 to 50 minutes.