Preheat the Oven: Set your oven to 350°F (175°C) and grease a 9x13-inch casserole dish with non-stick spray to ensure easy cleanup later.
Soften Butter and Cream Cheese: Microwave the cubed butter and cream cheese for about 20-30 seconds until soft, then whisk together until smooth and creamy.
Mix the Casserole Base: In a large mixing bowl, combine the cooked chicken, cooked rice, softened butter-cream cheese mixture, cream of chicken soup, minced garlic, Italian dressing mix, chicken stock, and half of the shredded Colby Jack cheese. Add salt and pepper to taste. Stir until everything is fully combined.
Assemble the Casserole: Evenly spread the chicken and rice mixture into your prepared casserole dish.
Top with Cheese: Sprinkle the remaining Colby Jack cheese over the top to create a cheesy crust.
Bake: Cover the dish with aluminum foil and bake in the preheated oven for 20-25 minutes, or until the cheese is melted and the casserole is bubbling around the edges.
Finishing Touches: Remove from the oven and allow the casserole to rest for about 5 minutes. Take off the foil, garnish with fresh parsley, and serve warm.
Enjoy this comforting and cheesy casserole!