This recipe is filled with everything you love about beef and broccoli: a thick and flavorful sauce, perfectly cooked beef, and fresh broccoli. For our version of this hearty dish, we set out to achieve perfectly cooked, crisp vegetables and flavorful meat. Our cast-iron skillet was a surprisingly perfect tool for stir-frying; when we got it ripping hot, we could sear the meat and vegetables quickly without overcooking them. For the meat, flank steak offered the best beefy taste, and slicing it thin against the grain made it tender. We cooked the beef in two batches over medium heat to make sure that it browned and didn't steam. Then we cooked the broccoli until crisp-tender using a combination of methods—sautéing and steaming—and added some red bell pepper for sweetness and color. For the sauce, a flavorful combination of oyster sauce, chicken broth, dry sherry, brown sugar, and toasted sesame oil, lightly thickened with cornstarch, clung to the beef and vegetables without getting gloppy. From: https://www.americastestkitchen.com/recipes/9892-cast-iron-stir-fried-beef-and-broccoli
FOR THE SAUCE: Whisk all ingredients together in bowl.
FOR THE STIR-FRY: Combine beef and soy sauce in bowl, cover, refrigerate, and let marinate for at least 10 minutes or up to 1 hour. Drain beef and discard liquid. In separate bowl combine garlic, ginger, and 1 teaspoon oil.
Heat 12-inch cast-iron skillet over medium heat for 5 minutes.
Add 1 tablespoon oil and heat until just smoking.
Add half of beef, break up any clumps, and cook, without stirring, for 1 minute.
Stir beef and continue to cook until browned, about 2 minutes; transfer to bowl.
Repeat with 1 tablespoon oil and remaining beef; transfer to bowl.
Heat 1 tablespoon oil in now-empty skillet over medium-high heat until just smoking.
Add broccoli and cook for 30 seconds.
Add ⅓ cup water, cover, and reduce heat to medium.
Steam broccoli until crisp-tender, about 2 minutes; transfer to paper towel–lined plate.
Wipe skillet clean with paper towels.
Heat remaining 2 teaspoons oil in now-empty skillet over medium-high heat until just smoking.
Add bell pepper and cook, stirring often, until spotty brown, about 1½ minutes.
Clear center of skillet, add garlic mixture, and cook, mashing mixture into skillet, until fragrant, about 30 seconds.
Add broccoli, beef, and any accumulated beef juices and toss to combine.
Whisk sauce to recombine, then add to skillet.
Cook, stirring constantly, until sauce is thickened, about 30 seconds.
Transfer to platter, sprinkle with scallions, and serve.