01 - Combine the sliced beef with 1 tbsp soy sauce, 1 tbsp cornstarch, and 1 tsp sesame oil in a bowl. Toss thoroughly to coat and let marinate for 10 minutes at room temperature.
02 - Whisk together the soy sauce, oyster sauce, hoisin sauce, cornstarch, brown sugar, broth, rice vinegar, and black pepper in a small bowl until the cornstarch and sugar dissolve completely. Set aside.
03 - Heat 1 tbsp vegetable oil in a large wok or skillet over high heat until shimmering. Add broccoli florets and sliced red bell pepper, stir-frying for 2–3 minutes until bright green and crisp-tender. Transfer vegetables to a plate and reserve.
04 - Add the remaining 1 tbsp oil to the hot pan. Arrange the marinated beef in a single layer without overcrowding. Sear for 1–2 minutes per side until well-browned but still pink inside.
05 - Add the minced garlic and ginger to the pan with the beef. Stir-fry constantly for 30 seconds until fragrant, being careful not to burn the garlic.
06 - Return the cooked vegetables to the pan. Toss everything together briefly, then pour in the prepared garlic sauce. Stir continuously for 1–2 minutes as the sauce bubbles and thickens to coat all ingredients evenly.
07 - Transfer the beef and broccoli stir fry to a serving platter or individual plates. Serve immediately while hot, accompanied by steamed white rice or noodles.