Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
Microwave frozen mac and cheese according to package directions.
Stir together macaroni, mac and cheese, milk and pepper in prepared dish. Mix well. Microwave on high 2 minutes, until heated through. Sprinkle with Cheddar and Parmesan and place under oven broiler. Broil until cheese is melted and beginning to brown, 2 to 5 minutes.
