In a large skillet, heat a bit of sesame oil over medium heat.
Add the diced onion and sauté until translucent.
Toss in the minced garlic and ground ginger, stirring until fragrant.
Add the ground beef, breaking it apart as it cooks. Season with salt, black pepper, and optional red pepper flakes.
Once the beef is browned, drain any excess fat.
Stir in the soy sauce and rice vinegar, mixing well to combine.
Add the shredded cabbage to the skillet, cooking until just tender, about 3-4 minutes.
Taste and adjust seasoning if necessary.
Serve hot, garnished with green onions and sesame seeds if desired.
