CRUST:
1 cup all-purpose flour
1/2 teaspoon salt
5 tablespoons cold butter, cubed
3 tablespoons cold water
FILLING:
1-1/2 cups chicken broth
2 cups peeled cubed potatoes
1 cup sliced carrots
1/2 cup sliced celery
1/2 cup chopped onion
1/4 cup all-purpose flour
1-1/2 cups whole milk
2 cups shredded sharp cheddar cheese
4 cups cubed cooked chicken
1/4 teaspoon poultry seasoning
Salt and pepper to taste

For crust, in a small bowl, combine flour and salt. Cut butter in flour until mixture resembles coarse crumbs. Gradually add the water, mixing gently with a fork. Gather into a ball. Cover and chill at least 30 minutes.
For filling, place broth in a Dutch oven; bring to a boil over high heat. Add vegetables. Reduce heat; simmer until vegetables are tender, 10-15 minutes.
In a small bowl, combine flour and milk; stir into broth mixture. Cook and stir over medium heat until slightly thickened and bubbly. Stir in cheese, chicken, poultry seasoning, salt and pepper. Heat until cheese melts. Spoon into a 10-in. cast-iron or other ovenproof skillet. Set aside.
On a lightly floured surface, roll dough for crust to fit top of casserole, trimming edges as necessary. Place on casserole over filling; seal edges. Make several slits in center of crust for steam to escape.
Bake at 425 degrees until golden brown, about 40 minutes.