In a large skillet over medium heat, cook beef, onion, soy sauce and garlic until beef is brown and juices run clear.
While beef is cooking, 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.
Return cooked pasta to its pot over low heat; stir in milk and butter. Stir in beef mixture until well combined. Stir in cheese slices, one at a time, until melted. Serve at once.
