Deep-Dish Chicken Potpie

In a bowl, combine flour and salt; cut in butter until mixture resembles coarse crumbs. Add water, 1 tablespoon at a time, stirring with a fork until a ball forms. Divide pastry into thirds. On a floured surface, roll two-thirds of the pastry to fit an ungreased 2-qt. baking dish; line dish with pastry. For filling, melt butter in a large saucepan; stir in flour until smooth. Add cream, broth, salt, thyme and pepper. Bring to a boil; boil for 2 minutes, stirring constantly. Stir in chicken, peas, potatoes, carrots and onion. Pour into prepared dish. Roll out remaining pastry to fit top of dish. Place over filling; seal edges. Cut slits in top; brush with milk. Bake at 350 degrees F for 1 hour or until vegetables are tender. ');