1 ½ cups water
¼ cup butter
1 (6 ounce) package quick-cooking stuffing mix (such as Stove Top(R)), or more to taste
1 tablespoon butter
1 onion, diced
3 stalks celery, diced, or more to taste
1 (10.75 ounce) can cream of chicken soup
1 (8 ounce) container sour cream
½ (10.5 ounce) can cream of mushroom soup
1 whole cooked rotisserie chicken – skinned, boned, and meat shredded
salt and ground black pepper to taste
Preheat oven to 375 degrees F (190 degrees C). Spray a 9×13-inch baking dish with cooking spray.
Bring water and 1/4 cup butter to a boil in a saucepan; stir in stuffing mix. Remove saucepan from heat, cover, and let sit until water is absorbed, about 5 minutes. Fluff stuffing with a fork.
Heat 1 tablespoon butter in a skillet over medium heat; cook and stir onion and celery until softened, 5 to 10 minutes.
Mix cream of chicken soup, sour cream, and cream of mushroom soup together in a bowl.
Spread shredded chicken into the bottom of the prepared baking dish. Layer onion mixture over chicken and season with salt and pepper; top with soup mixture. Spread stuffing over soup mixture layer.
Bake in the preheated oven until lightly browned and bubbling, about 1 hour.