Heat the oven to 350°F (175°C) and coat a 9x13-inch baking dish with nonstick spray.
In a medium bowl, whisk together the sour cream, ranch seasoning, minced garlic, black pepper, Alfredo sauce and 1 cup of the shredded mozzarella until smooth and combined.
Fold the cooked penne and chopped chicken into the sauce mixture, stirring gently so the pasta and chicken are evenly coated.
Transfer the pasta and chicken blend to the prepared baking dish, spreading it into an even layer.
Evenly scatter the remaining 1 cup of mozzarella over the casserole and top with the chopped bacon pieces.
Cover the dish with foil and bake for about 20 minutes, or until the casserole is bubbling and the cheese has melted.
Remove the foil, sprinkle with chopped parsley if desired, let sit a few minutes, then serve warm.