Heat oil in a large skillet or wok over medium-high heat.
Add the beef strips and garlic; cook until the beef is browned. Once done, season to taste with salt and pepper, and remove from skillet.
Adde additional oil to the skillet if needed. Cook pepper and onion in skillet until they are tender.
Add the broth, soy sauce, mushrooms, and optional xanthan gum and baby corn (if using).
Cook and stir until mushrooms are softened.
Stir in the beef and continue cooking until heated throughout.
Baby corn will add another 1-2 grams net carbs per serving. Other keto friendly vegetables like broccoli can be added or used in place of the peppers and or mushrooms.For a thick sauce, sprinkle in about ¼ to ½ teaspoon xanthan gum. Adding in about a 1 to 3 teaspoons of coconut flour or almond flour to the soy sauce before adding may also work.Flank steak is a popular cut to use in beef stir fry so it can be used instead of the sirloin.