For the Beef Marinade: - 1 lb (450g) beef sirloin steak, thinly sliced against the grain - 2 tablespoons soy sauce - 2 cloves garlic, minced - 1 teaspoon grated ginger - 1 tablespoon rice vinegar For the Stir-Fry: - 1 tablespoon olive oil - 2 cups broccoli florets - Salt and pepper, to taste For the Sauce: - 1/4 cup soy sauce - 2 tablespoons oyster sauce (optional) - 1 tablespoon rice vinegar - 1 tablespoon sesame oil - 1 tablespoon cornstarch (or arrowroot powder) - 1/4 cup water

In a bowl, combine the thinly sliced beef sirloin steak with soy sauce, minced garlic, grated ginger, and rice vinegar. Toss to coat the beef evenly. Let it marinate for at least 15-30 minutes.

In a separate bowl, whisk together soy sauce, oyster sauce (if using), rice vinegar, sesame oil, cornstarch (or arrowroot powder), and water until well combined. Set aside.

Heat olive oil in a large skillet or wok over medium-high heat.
Add the marinated beef to the skillet and cook, stirring frequently, until browned and cooked through. This should take about 3-4 minutes.

Remove the beef from the skillet and set aside.
In the same skillet, add the broccoli florets. Stir-fry for 3-4 minutes or until the broccoli is tender-crisp.

Season the broccoli with salt and pepper to taste.

Return the cooked beef to the skillet with the broccoli.

Pour the prepared sauce over the beef and broccoli mixture in the skillet.

Cook, stirring constantly, until the sauce thickens and coats the beef and broccoli evenly. This should take about 1-2 minutes.