Slumgullion

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 and place in large saucepan.
Meanwhile, in a large skillet, brown beef over medium heat; just before beef is browned, stir in onion.
Add beef mixture to pasta, and stir in tomato sauce, mushrooms, garlic, salt, pepper and stewed tomatoes. Cook over low heat, 10 to 15 minutes, or until heated through.