Slice the beef into thin strips against the grain.
In a mixing bowl, combine soy sauce, garlic, ginger, sesame oil, and apple cider vinegar to create a marinade.
Add the beef to the marinade and let it sit for at least 30 minutes.
Place the marinated beef into the crockpot and pour in the beef broth.
Set the crockpot on low heat and cook for 4-6 hours, or until the beef is tender.
About halfway through, stir the beef to distribute the sauce evenly.
Add the broccoli florets to the crockpot and stir.
Cover and cook for an additional 30 minutes or until the broccoli is tender.
If desired, thicken the sauce by stirring in xanthan gum or heavy cream.
Taste and adjust seasoning with salt and pepper as needed.
Serve hot and enjoy!