Chicken Pot Pie

1. Preheat oven to 375°F (190°C). Melt butter in a large skillet over medium heat. Add onion and celery; cook until softened, about 5 minutes. Stir in flour and cook for 1 minute. 2. Gradually whisk in chicken broth and milk until smooth. Stir in cream of chicken soup, shredded chicken, frozen vegetables, salt, and pepper. Bring to a simmer and cook until thickened, about 5-7 minutes. 3. Pour the chicken mixture into a 9-inch pie dish. Top with one pie crust, crimping the edges to seal. Cut slits in the top crust for ventilation. 4. Bake for 30-35 minutes, or until the crust is golden brown and the filling is bubbly. Let stand for 10 minutes before serving.