Preheat your oven to 350°F and generously spray a 9x13” casserole dish with cooking spray.
In a microwave-safe bowl, soften the cream cheese and butter in the microwave for 20-30 seconds. Whisk until smooth.
In a large mixing bowl, combine the cooked chicken, rice, butter and cream cheese mixture, cream of chicken soup, garlic, Italian dressing mix, chicken stock, half of the shredded cheese, and salt and pepper. Mix well until everything is evenly combined.
Transfer the chicken and rice mixture into the prepared casserole dish and top with the remaining shredded cheese.
Cover the dish with foil and bake in the preheated oven for 20-25 minutes, until the cheese is melted and the casserole is bubbling.
Remove from the oven and let the casserole cool for 5 minutes before removing the foil.