Brown the Beef: In a large skillet, heat over medium-high heat and add the ground beef. Cook for about 5-7 minutes, breaking it apart with a spatula until it's browned and no longer pink. Drain any excess fat.

Sauté the Onions: Add the finely diced onion to the skillet and sauté for 2-3 minutes until translucent and tender.

Infuse with Garlic and Ginger: Stir in the minced garlic and ground ginger, cooking for about 1 minute until fragrant.

Add the Cabbage: Mix in the shredded cabbage and cook for 4-5 minutes until wilted but slightly crunchy.

Combine with Sauce: Whisk together soy sauce, sesame oil, rice vinegar, and optional red pepper flakes. Pour the mixture over the beef and cabbage, stirring to coat. Simmer for 2-3 minutes.

Garnish and Serve: Remove from heat and garnish with sliced green onions and toasted sesame seeds before serving immediately.