Whisk together the soy sauce, sesame oil, garlic, ginger, brown sugar, cornstarch, and water in a small bowl until the cornstarch is fully dissolved. Set aside.
Heat the vegetable oil in a large pot or wok over medium-high heat. Season the beef slices with salt and pepper, and add them to the pot. Cook for 2-3 minutes until browned, then remove the beef and set it aside.
Add the broccoli florets and a splash of water in the same pot. Cover with a lid and let the broccoli steam for about 3 minutes or until it is bright green and tender.
Return the beef to the pot with the broccoli and pour the sauce mixture over the top. Stir well to combine and cook for another 2-3 minutes until the sauce thickens and everything is heated.
Serve the beef and broccoli over cooked rice and sprinkle with red pepper flakes if desired.
Prep: 10 minutes
Cook: 15 minutes
Total Time: 25 minutes
Servings: 4Cooking Time: 15 minutesTotal Time: 25 minutesKcal: Approximately 350 per serving