In a mixing bowl, combine the soy sauce, sesame oil, minced garlic, minced ginger, erythritol, and beef broth. If using cornstarch for a thicker sauce, dissolve it in the beef broth before adding it to the sauce mixture. Whisk until well combined and set aside.
Heat a large skillet or wok over medium-high heat. Add the beef slices in a single layer, cooking for about 2-3 minutes until browned. Avoid overcrowding the pan, and cook in batches if necessary.
Once the beef is cooked, remove it from the skillet and set it aside.
In the same skillet, add the broccoli florets. Stir-fry for about 4-5 minutes until they are bright green and tender-crisp.
Return the beef to the skillet with the broccoli. Pour the sauce over the beef and broccoli and stir well to coat. Cook for an additional 2-3 minutes until the sauce has thickened and everything is heated through.
Season with salt and pepper to taste, and garnish with sesame seeds if desired.
Serve hot and enjoy your Keto Low Carb Beef and Broccoli dish!