Heat a wok or large skillet over medium-high heat, and add oil. Saute garlic for about 5 seconds, then add ground beef. Stir-fry until beef is evenly brown, 5 to 7 minutes; drain excess fat.
Stir in cabbage and onion, and cook until vegetables are tender and beef is fully cooked. Stir in soy sauce. Mix together cornstarch and water, and stir in. Season with pepper; add salt to taste. Cook, stirring, until sauce has thickened. Good with cornbread and spinach salad.