Heat a large skillet over medium heat for about 1 minute. Add the ground beef and break it into smaller pieces with a spatula. Cook for 5-7 minutes until fully browned with no pink remaining.

Drain any excess fat from the skillet by carefully tilting it and spooning out accumulated grease, leaving just enough to keep the meat moist.

Add the diced onion and minced garlic to the skillet. Cook for 2-3 minutes, stirring occasionally, until soft and fragrant.

Stir in the shredded cabbage and cook for about 5 minutes, stirring occasionally, until the cabbage wilts down and becomes tender but still has a slight bite.

Pour in the soy sauce, sesame oil, and rice vinegar. Add the ground ginger, red pepper flakes (if using), salt, and black pepper. Mix everything thoroughly.

Continue cooking for an additional 2-3 minutes, stirring frequently, to allow the flavors to meld together. Taste and adjust seasonings as needed.

Remove from heat and garnish with sliced green onions and toasted sesame seeds. Serve immediately or store for meal prep.