Preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius). Lightly grease a 9×13 inch baking dish.
Cook the penne pasta according to package directions until al dente. Drain well.
In a large bowl, combine the cooked pasta, shredded chicken, Alfredo sauce, heavy cream, Parmesan cheese, garlic powder, pepper, and salt. If using, stir in the thawed broccoli. Mix until everything is evenly coated.
Pour the pasta mixture into the prepared baking dish, spreading it into an even layer.
Sprinkle the 2 cups of mozzarella cheese evenly over the top of the pasta mixture.
Bake for 20 to 25 minutes, or until the sauce is bubbly and the mozzarella cheese is melted and lightly golden brown.
Remove from the oven and let it rest for 5 minutes before serving. Garnish with fresh parsley.
Notes
For a richer sauce, you can make your own Alfredo sauce instead of using jarred.
Use rotisserie chicken to save time on cooking the chicken.
If you prefer a thinner sauce, add a splash of milk or reserved pasta water before baking.
Mushrooms or cooked spinach are good additions if you want more vegetables.