Heat a large skillet over medium heat with 1 tablespoon sesame oil.
Arrange the sliced beef in a single layer and cook for about 5 minutes until browned and cooked through.
Remove the beef from the skillet and set aside.
Add another tablespoon of sesame oil to the skillet.
Add the broccoli florets along with 2 tablespoons of water.
Cover and steam for 3–5 minutes until the broccoli is tender-crisp.
In a small bowl, whisk together the remaining sesame oil, water, soy sauce, brown sugar, cornstarch, grated ginger, garlic, crushed red pepper flakes, and black pepper.
Return the beef to the skillet with the broccoli.
Pour the sauce over everything and stir well.
Reduce the heat and simmer for 2–3 minutes until the sauce thickens and coats the beef and broccoli. This Healthy Beef and Broccoli Stir Fry Recipe is best served immediately over steamed rice or brown rice and sprinkled with sesame seeds.