1. Prep Your Ingredients: Slice the beef sirloin against the grain into thin strips. Chop the broccoli into bite-sized florets.
2. Whip Up the Sauce: In a small bowl, combine soy sauce, brown sugar, minced garlic, ginger (if using), and sesame oil until well mixed.
3. Sauté the Beef: Heat cooking oil in a large skillet over medium-high heat. Cook the sliced beef in a single layer until browned—about 3 minutes per side.
4. Add Broccoli: Toss in chopped broccoli and stir-fry with the beef for another 3–5 minutes until bright green yet crunchy.
5. Pour in the Sauce: Drizzle teriyaki sauce over the beef and broccoli mixture. Toss until well-coated and heated through—approximately 2 minutes.
6. Serve It Up: Transfer to plates over steamed rice or noodles and enjoy!
