Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish or casserole pan with cooking spray.
If not already done, boil the pasta until al dente. In the last 2 minutes of cooking, toss in the broccoli to soften slightly. Drain and set aside.
In a large bowl, mix the cooked chicken, pasta, broccoli, cream of chicken soup, milk, sour cream, garlic powder, onion powder, salt, pepper, and 1 cup of shredded cheddar cheese.
Pour the mixture into the prepared baking dish and spread evenly. Top with the remaining ½ cup of shredded cheddar and sprinkle with Parmesan or cracker crumbs if using.
Bake uncovered for 20–25 minutes, or until the casserole is bubbly and the top is lightly golden and crispy.
Let the dish sit for 5 minutes before serving. It will thicken slightly as it cools.