In a large skillet, heat a splash of oil over medium-high heat. Add the ground beef, breaking it apart, and cook for about 5-7 minutes until browned.

Add the diced onion to the skillet with the beef. Sauté for 2-3 minutes until the onions become translucent and fragrant.

Stir in the minced garlic and ground ginger and cook for an aromatic minute, stirring continuously.

Add the shredded cabbage to the skillet, stirring well to combine with the beef mixture. Cook for 4-5 minutes until the cabbage wilts but remains slightly crunchy.

In a small bowl, mix the soy sauce, sesame oil, rice vinegar, and optional red pepper flakes. Pour over the beef and cabbage and stir to coat evenly.

Garnish with sliced green onions and toasted sesame seeds if desired, and serve warm.