Combine first 4 ingredients in a medium saucepan; add water to cover. Bring to a boil. Cover; reduce heat, and simmer 20 minutes or until vegetables are tender. Drain.
Combine cooked vegetables, chicken, and parsley in a shallow 2 1/2-quart casserole. Set mixture aside.
Melt butter in a heavy saucepan; blend in flour. Cook over low heat until bubbly, stirring constantly. Gradually add broth and half-and-half; cook, stirring constantly, until thickened and bubbly. Stir in salt and pepper. Pour over vegetables and chicken in casserole.
Top with Sweet Potato Crust. Turn pastry edges under, and press firmly to rim of casserole to seal. Cut slits in top of pastry. Bake at 350° for 40 minutes or until pastry is browned.