Mushroom-Beef Spaghetti Sauce

In a large nonstick skillet, cook the beef, mushrooms and onion over medium heat until meat is no longer pink; drain. Transfer to a 3-qt. slow cooker. , Stir in the tomatoes, tomato paste, tomato sauce, broth, parsley, brown sugar, basil, oregano, salt and pepper. Cover and cook on low for 6-8 hours. Serve with spaghetti. Sprinkle with cheese if desired.