Chicken Pot Pie

Ingredients

1 (17.5 ounce) package frozen puff pastry, thawed
⅓ cup butter
½ medium onion, chopped
1 stalk celery, sliced
⅓ cup flour
1 teaspoon salt
½ teaspoon ground black pepper
½ teaspoon celery seed
1 cup milk
2 cups chicken broth
1 pound cooked chicken breast, cubed
1 (12 ounce) package frozen mixed vegetables

Directions