Prep the beef. Freeze the steak for 20–30 minutes to firm it up. Slice thinly against the grain. Pat dry with paper towels and season lightly with salt and pepper.

Mix the sauce. In a bowl, whisk tamari or coconut aminos, broth, vinegar, keto sweetener, and fish sauce if using. If you plan to thicken, sprinkle in xanthan gum while whisking to avoid clumps. Set aside.

Prep the veggies. Cut broccoli into bite-size florets. Mince the garlic, grate the ginger, and slice green onions, keeping white and green parts separate.

Flash-steam the broccoli. In a large skillet or wok over medium-high heat, add a splash of water and the broccoli. Cover for 2–3 minutes until bright green and crisp-tender. Remove and set aside. Wipe out any excess water.

Stir-fry the beef. Heat 1 tablespoon oil over high heat. Add half the beef in a single layer. Sear 60–90 seconds per side until browned but not overcooked. Remove to a plate and repeat with remaining beef, adding more oil if needed.

Sauté aromatics. Lower heat to medium-high. Add remaining oil if the pan is dry. Toss in garlic, ginger, and the white parts of the green onions. Stir for 30 seconds until fragrant.

Combine everything. Return beef and broccoli to the pan. Pour in the sauce. Toss and cook 1–2 minutes until the sauce thickens slightly and coats the beef and broccoli. Add crushed red pepper if you like heat.

Finish and serve. Turn off heat. Stir in sesame oil and the green parts of the onions. Taste and adjust seasoning. Garnish and serve hot.