Make the sauce. In a small bowl, whisk soy sauce, oyster sauce, chili garlic sauce, rice vinegar, brown sugar, broth, and cornstarch until smooth. Set aside.
Prep the vegetables. Thinly slice the cabbage and onion.
Mince the garlic and grate the ginger. Keep everything close—stir fry moves fast.
Brown the beef. Heat a large skillet or wok over medium-high heat. Add 1 tablespoon oil and the ground beef.
Break it up with a spatula and cook until browned and slightly crisp at the edges, about 5–7 minutes. Season with a pinch of salt and pepper.
Drain if needed. If there’s a lot of fat, spoon off excess so the pan isn’t greasy. Leave about 1–2 teaspoons for flavor.
Sauté aromatics. Push the beef to one side.
Add remaining oil to the empty side. Add onion, garlic, and ginger. Cook 1–2 minutes until fragrant and the onion starts to soften.
Add cabbage. Toss in the sliced cabbage (and carrot or bell pepper if using).
Stir fry 4–6 minutes, until the cabbage softens but still has a slight bite. Don’t overcook—it should stay a bit crisp.
Combine and sauce. Stir the beef and vegetables together. Give the sauce a quick stir and pour it into the pan.
Cook 1–2 minutes, tossing, until the sauce thickens slightly and coats everything.
Finish with sesame. Turn off the heat. Stir in sesame oil and green onions. Taste and adjust seasoning: add more soy for salt, chili sauce for heat, or a splash of vinegar for brightness.
Serve. Garnish with sesame seeds and extra green onions.
Serve as is, with rice, or over noodles.