In a shallow dish, combine the flour, salt, and pepper. Dredge the beef schnitzel slices in the flour mixture, shaking off any excess. Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the minced garlic and grated ginger to the hot oil. Stir-fry for about 30 seconds until fragrant. Add the coated beef schnitzel slices to the skillet and cook for 2-3 minutes per side until golden brown and cooked through. Remove the cooked beef from the skillet and set aside
In the same skillet, add the sliced onion, bell pepper, carrot, and broccoli florets. Stir-fry for 3-4 minutes until the vegetables are slightly tender.In a small bowl, whisk together the soy sauce, oyster sauce, hoisin sauce, and sesame oil. Pour the sauce mixture over the vegetables in the skillet.
Add the cooked beef schnitzel slices back to the skillet with the vegetables. Stir-fry everything together for another 2-3 minutes, ensuring the beef and vegetables are coated evenly in the sauce.
Taste and adjust the seasoning with salt and pepper, if needed. Remove the skillet from the heat and transfer the beef schnitzel stir fry to serving plates or bowls.
Garnish with sliced green onions and sesame seeds, if desired. Serve hot and enjoy the flavorful twist of Beef Schnitzel Stir Fry!