In a large skillet, heat over medium-high heat and add the lean ground beef. Brown the meat for about 5 to 7 minutes, breaking it into smaller pieces with a spatula. Cook until thoroughly browned and no longer pink. Drain excess fat.

Reduce the heat to medium, add finely diced onion and minced garlic to the skillet. Sauté for 2 to 3 minutes until onion softens and becomes translucent.

Toss shredded cabbage into the skillet, stirring everything together. Cook for about 5 minutes, or until it begins to wilt but still has a slight crunch.

Pour in soy sauce, sesame oil, rice vinegar, ground ginger, and red pepper flakes. Stir well to combine all ingredients. Cook for another 2 to 3 minutes until sauce thickens slightly.

Transfer the dish to serving plates and garnish with sliced green onions and toasted sesame seeds. Serve hot and enjoy.