Preheat oven to 350°. Cook rice according to package directions. In a small skillet, saute celery and onion in 1 tablespoon butter until tender. Stir in the soup, mushrooms and prepared rice., Sprinkle inside and outside of hens with salt and pepper. Stuff with rice mixture. Place on a rack in a greased shallow roasting pan; cover with foil. , Bake at 350° for 40 minutes. Remove foil. Melt remaining butter; brush over hens. Bake 25-35 minutes longer or until juices run clear and a thermometer reads 180° for hens and 165° for stuffing.