Melt butter in a lightly greased 13- x 9-inch baking dish in a 425° oven.
Sprinkle chicken with salt and pepper. Dip chicken in 1/2 cup buttermilk, and dredge in flour.
Arrange chicken, breast side down, in baking dish.
Bake at 425° for 25 minutes. Turn chicken, and bake 10 more minutes.
Stir together remaining 1 cup buttermilk and cream of mushroom soup; pour over chicken, and bake 10 more minutes, shielding chicken with aluminum foil to prevent excessive browning, if necessary. Drizzle gravy over chicken and Whipped Celery Potatoes. Garnish, if desired.
*4 skinned and boned chicken breast halves may be substituted. Bake chicken at 425º for 15 minutes. turn, and bake for 10 minutes.
Note: Light butter; nonfat buttermilk; and reduced-sodium, reduced-fat cream of mushroom soup may be substituted.