Simmer chicken in water with onion, celery, carrots and salt until tender (about 3 hours).
Remove chicken from bones and cut into cubes, discarding the skin. Strain broth and measure, adding water to make 3 cups. Thicken broth with 4 Tbsp flour mixed with 1/4 cup water. Adjust seasonings with a dash of white pepper and more salt if necessary. Add chicken, carrots and potatoes. Spoon into 6 individual casserole dishes or a 2-quart casserole.
Roll pastry about 1/4-inch thick and top the casserole, sealing the edges. Make several slashes in the pastry to allow the steam to escape. Bake in a hot oven (400° F) for about 30 minutes or until golden brown.
NOTE: Biscuit dough (rolled thin) or individual biscuits may be used for the topping. Frozen peas (defrosted) may also be added.Makes 4 Source: