Preheat oven to 350 degrees and spray a 9x13 baking dish with cooking spray.
Prepare Minute Rice according to package directions and set aside. Microwaving works great if you want to keep it simple.
In a large mixing bowl combine the shredded chicken, prepared rice, cream of chicken soup, softened cream cheese, Italian dressing seasoning packet, garlic powder, and chicken stock. Stir until everything is fully combined and creamy with no lumps of cream cheese visible.
Fold in 1.5 cups of the Colby Jack cheese and stir until evenly distributed throughout the mixture.
Pour the mixture into the prepared baking dish and spread it into an even layer.
Sprinkle the remaining 0.5 cup of Colby Jack cheese evenly over the top.
Add the Panko breadcrumbs in an even layer over the cheese.
Dot the top with the sliced butter pieces, distributing them as evenly as possible across the entire surface.
Bake uncovered for 25 to 30 minutes until the edges are bubbly, the cheese is fully melted, and the breadcrumb topping is deep golden brown and crispy.
Let the casserole rest for 5 minutes before serving. Garnish with fresh chopped parsley if desired.