Preheat the oven to 375 degrees. Coat a 3 quart baking dish with cooking spray.
Melt the butter in a large pan over medium heat. Add the garlic and cook for 30 seconds. Whisk in the flour and cook for 1 minute.
Pour in the milk and cream, then simmer, whisking constantly, until sauce has just thickened.
Add the parmesan cheese and 1/2 cup shredded mozzarella to the milk mixture, along with salt and pepper to taste.
Stir until cheese has melted.
Place the pasta and chicken in a large bowl. Pour the sauce over the top, and toss to coat evenly.
Pour the pasta mixture into the prepared pan, and top with remaining mozzarella cheese.
Bake, uncovered, for 20 minutes or until pasta is bubbly and cheese has just started to brown.
Sprinkle parsley over the top, then serve.