Preheat the oven to 400 degrees F (200 degrees C).Advertisement
Melt butter in a medium skillet over medium heat. Whisk in flour until smooth. Add parsley, salt, and garlic powder. Whisk and cook for 1 minute. Pour in broth and milk. Cook, whisking often, until thickened and smooth, 7 to 12 minutes. Add 1/2 cup mozzarella cheese and all the Parmesan; stir until melted.
Beat cream cheese in a medium bowl until smooth. Add the Alfredo sauce and beat until combined. Stir in chicken. Spread mixture into a medium baking dish and top with remaining 1/2 cup mozzarella cheese.
Bake in the preheated oven until bubbly and beginning to brown, 15 to 20 minutes.