Preheat oven to 350º F. Spray a 9×13 baking dish with cooking spray.
In a large bowl whisk together the the cream of mushroom soup, cream of chicken soup, cream of celery soup, diced celery, and one soup can of chicken broth. (Fill an empty can of soup with chicken broth to the rim.) Stir in the rice and 1/4 teaspoon black pepper.
1 can Cream of chicken soup, 1 can Cream of mushroom soup, 1 can Cream of celery soup, 1 1/3 cup Reduced sodium chicken stock, 2 stalks Celery, 1 cup Long grain white rice
Pour the rice mixture into the prepared pan, cover tightly with aluminum foil, and bake for 1 1/2 hours. Uncover and stir the rice mixture from bottom to top. Increase the oven temperature to 400º F.
Season the chicken breast with kosher salt and pepper on both sides. Place the seasoned chicken on top of the rice mixture, and top each piece with two 1/2 tablespoons of unsalted butter. Cover and bake for another 20 minutes.
2 large Boneless skinless chicken breast, 1/2 tsp Kosher salt, 3/4 tsp Black pepper, 1/4 cup Unsalted butter
Uncover stir the rice again and bake for another 10 minutes or until the internal temperature of the chicken is at least 163º F.
Remove from the oven and let it rest for at least 10 minutes. This allows the rice to absorb any remaining liquid and the chicken to increase in temp to 165º F. Season to taste with additional salt and pepper.