In a large skillet or wok, heat the sesame oil over medium-high heat. Add the ground beef and cook until browned, breaking it apart with a spatula, about 5-7 minutes. Drain excess fat if necessary.
Add the sliced onion, minced garlic, and ginger to the skillet. Stir-fry for 2-3 minutes until the onion is translucent.
Stir in the shredded cabbage and cook for another 5 minutes, stirring occasionally, until the cabbage is tender.
Pour in the soy sauce, rice vinegar, sugar, and black pepper. Mix well and cook for an additional 2 minutes to heat through.
Remove from heat and garnish with chopped green onions and sesame seeds before serving.