Toss the beef strips with the soy sauce and sherry. Set aside until ready to use.
Combine the sauce ingredients until the cornstarch is dissolved. Set aside until ready to use.
Heat the oil over high heat in a wok or large heavy skillet. Once very hot, add the beef and fry until lightly browned, about 2 minutes. Add the onions, garlic and ginger and fry for another minute. Add a little more oil if necessary. Add the broccoli and fry for another minute or until crisp-tender. Stir in the bean sprouts. Stir in the sauce and simmer for another minute.
Serve immediately with steamed rice.
Notes
*The quick cooking times assume you're using a wok or heavy skillet over very high heat (some cooktops don't have the capacity to go as high as high-heat wok cooking requires). You may need to increase the cooking time accordingly.