Start by preheating your oven to 350°F (175°C). Lightly spray a 9×13-inch casserole dish with non-stick spray or brush it with butter. This prevents sticking and makes cleanup easier.
Place the cubed butter and cream cheese in a microwave-safe bowl. Heat for about 20–30 seconds until softened, then whisk until smooth. This will make the sauce extra creamy and easy to mix later.
In a large bowl, mix together the cooked chicken, cooked rice, cream of chicken soup, minced garlic, Italian dressing mix, chicken broth, and the butter-cream cheese mixture. Stir until everything is evenly combined, then season with salt and pepper to taste.
Pour the mixture into your prepared casserole dish, spreading it evenly. Sprinkle half of the shredded Colby Jack cheese into the mixture, and save the rest for topping. Smooth the surface and make sure it’s evenly distributed.
Cover the dish with foil and bake for about 20–25 minutes. When the cheese on top is melted, bubbly, and slightly golden, remove the foil and let it bake uncovered for the last few minutes to achieve a beautiful crust.
Let the casserole rest for 5 minutes after removing it from the oven. This allows the sauce to thicken slightly. Garnish with fresh parsley before serving.