Fill a pot with lightly salted water and bring to a rolling boil over high heat. Once the water is boiling, stir in the macaroni, and return to a boil. Cook the pasta uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 8 minutes. Drain well in a colander set in the sink.
Slice up the sausage, place on a microwave-safe plate, and heat the sausage just until hot, about 30 seconds. Mix the sausage slices into the hot macaroni, and stir in the milk, butter, Parmesan cheese, and mozzarella cheese. Stir until the cheese is melted, and serve.
