Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Once the water is boiling, stir in the rotini, and return to a boil. Cook uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 10 minutes. Drain well in a colander set in the sink.
Preheat an oven to 375 degrees F (190 degrees C).
In a bowl, mix soup, broccoli, chicken, and milk. Season with garlic powder and pepper. Transfer to a baking dish and top with Cheddar cheese.
Cover and bake 20 minutes in the preheated oven. Remove cover and continue baking 10 minutes, until bubbly.
