Marinate the Steak:

In a bowl, whisk together soy sauce, oyster sauce, hoisin, brown sugar, rice vinegar, garlic, ginger, and sesame oil. Add steak cubes and toss to coat. Let marinate for 30 minutes (or at least 10 minutes for quicker prep).

Add Cornstarch:

Just before cooking, sprinkle cornstarch over the marinated steak and toss to coat. This helps create a crisp crust when seared.

Sear the Steak Bites:

Heat vegetable oil in a large skillet or wok over medium-high heat. Once hot, add steak bites in a single layer (work in batches if needed). Sear for 2–3 minutes per side until browned and caramelized on the outside and medium-rare inside.

Serve:

Remove from heat and transfer to a serving plate. Garnish with green onions, sesame seeds, or a drizzle of sriracha if desired.