Thinly slice the scallion greens on a bias and reserve for garnishing. The remaining scallion whites can be finely chopped for the sauce base.

In a mixing bowl combine the soy sauce, oyster sauce, ginger, chili flakes and salt.

Cut the flat iron into 1/2 inch strips, crosswise.

Gently mix the strips of beef into the marinade until well coated. Cover with plastic wrap and refrigerate. For the tastiest results, we suggest marinating the flat iron for 30 minutes. If you're in a hurry, you can skip this step.

In a small mixing bowl, whisk together the beef stock, oyster sauce, soy sauce, brown sugar, rice wine vinegar and lemon juice. Set aside for later use.

In a small bowl, stir the cornstarch and water until completely incorporated. Reserve for thickening the sauce.

Add the oil and preheat the pan to 300°F/148°C (medium-low).

Add the garlic and scallion whites and sauté for 50 seconds. Stir frequently.

Reduce the temperature to 212°F/100°C (low), add the sauce base and season with black pepper. Bring to a gentle simmer before moving on to thickening the sauce.

Gradually whisk the slurry into the sauce base. Cook the sauce for 15- 20 seconds while continuously stirring until the sauce has thickened.

Using a rubber spatula, carefully transfer the sauce to a small bowl. To keep warm, wrap the bowl tightly with foil until ready to serve. Thoroughly wash and dry the pan before continuing to the next step.

Add the oil and preheat the pan to 400°F/204°C (medium-high). Tilt the pan to coat evenly.

Add the broccoli and sauté for 2 minutes and 30 seconds. Stir frequently.

Remove from the heat before seasoning the broccoli with kosher salt, chili flakes, and black pepper.

Using a pair of tongs, transfer the broccoli from the pan to a medium bowl and set aside. Thoroughly wipe the pan with a paper towel before continuing to the next step.

Add the oil and preheat the pan to 425°F/218°C (high). Tilt the pan to coat evenly.

Using a pair of tongs, place 8-10 strips of the flat iron to the pan making sure not to overcrowd the pan and sear for 1 minute and 30 seconds.

Flip and sear the second side of the flat iron for 1 minute and 30 seconds. Remove the flat iron and reserve for later use.

Reduce the temperature 325°F/162°C (medium). Add the sauce, broccoli, and steak back in the pan and stir well. Reheat the beef and broccoli for 30 seconds while stirring continuously.

Turn the heat off and remove the beef and broccoli to a dish for serving. Sprinkle the scallion greens over the beef and broccoli. Serve with steamed rice or enjoy all on its own!