Place the beef on a clean cutting board and use a sharp knife to slice it thinly against the grain. Cutting against the grain shortens the muscle fibers, which helps keep the beef tender instead of chewy. Try to make the slices fairly even so they cook at the same rate. If the beef feels difficult to slice, placing it in the freezer for about 15–20 minutes can make it firmer and easier to cut.

In a small mixing bowl, combine the sauce ingredients such as soy sauce (or coconut aminos), sesame oil, minced garlic, grated ginger, and a small pinch of keto-friendly sweetener if using. Sprinkle in the xanthan gum and whisk everything together until smooth. Mixing the sauce beforehand ensures the flavors blend evenly and makes it easier to pour directly into the pan later.

Heat a large skillet or wok over medium-high heat and add a small amount of cooking oil. Once the pan is hot, add the sliced beef in a single layer. Let it cook undisturbed for about 1–2 minutes so it develops a nice brown sear, then stir or flip the pieces and cook for another minute or two until the beef is mostly cooked through. Avoid overcrowding the pan so the beef sears instead of steaming.

Add the broccoli florets directly to the skillet with the beef. Stir everything together and cook for about 3–4 minutes, allowing the broccoli to become bright green and slightly tender while still maintaining a little crunch. If the pan seems dry, you can add a tablespoon of water to help the broccoli steam briefly.

Pour the prepared sauce over the beef and broccoli mixture. Stir well so the sauce coats everything evenly. Let the mixture simmer for about 1–2 minutes, stirring occasionally, until the sauce thickens slightly and clings to the beef and vegetables.

Remove the skillet from the heat and divide the beef and broccoli mixture into serving bowls. Finish by sprinkling sesame seeds or sliced green onions over the top for extra flavor and texture. Serve warm while the beef is tender and the sauce is glossy and flavorful.