Preheat your oven to 375°F. Grease a 9×13 inch baking dish lightly with cooking spray or butter.
In a large mixing bowl, combine the cooked pasta, chicken, Alfredo sauce, garlic parmesan sauce, half of the mozzarella cheese, and half of the Parmesan cheese. Season with salt and pepper to taste.
If needed, add about ½ cup of reserved pasta water to ensure the mixture is moist and saucy.
Transfer the mixture into the prepared baking dish, spreading it evenly.
Top with the remaining mozzarella and Parmesan cheeses.
Cover with aluminum foil and bake in the preheated oven for 20-25 minutes, until the cheese is melted and bubbly.
Optional: For a golden top, broil for 2-3 minutes, watching closely to prevent burning.

Let cool for 5 minutes, then garnish with fresh parsley if desired. Serve warm.