01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with cooking spray or butter.
02 - Bring a large pot of salted water to boil. Cook pasta until al dente according to package directions. Drain well and set aside.
03 - Steam broccoli florets until just tender, approximately 3-4 minutes. Drain thoroughly to remove excess moisture.
04 - In a large mixing bowl, combine cooked pasta, diced chicken, steamed broccoli, Alfredo sauce, milk, garlic powder, Italian herbs, and half the mozzarella and Parmesan cheeses. Season generously with salt and black pepper, mixing until evenly distributed.
05 - Transfer the pasta mixture to the prepared baking dish, spreading evenly. Sprinkle remaining mozzarella and Parmesan cheese across the surface in a uniform layer.
06 - Bake uncovered for 25-30 minutes until cheese is melted, bubbly, and golden brown on top.
07 - Allow the dish to rest for 5 minutes before serving to let the sauce set and make serving easier.