01 - Whisk together soy sauce, sesame oil, rice vinegar, sweetener if using, and red pepper flakes in a small bowl. Set aside.
02 - Heat 1 tablespoon of oil in a large skillet or wok over medium-high heat. Add sliced beef in a single layer and cook for 2-3 minutes until browned. Remove beef and set aside.
03 - Add remaining tablespoon of oil to skillet. Stir-fry broccoli florets for 3-4 minutes until bright green and just tender.
04 - Add minced garlic and grated ginger to skillet. Stir-fry for 30 seconds until fragrant.
05 - Return beef to skillet, pour in sauce, and toss to combine. Cook for 2-3 minutes until sauce thickens slightly and ingredients are heated through.
06 - Sprinkle sliced scallions over stir-fry and serve immediately.