Mix together the hoisin sauce, oyster sauce and water in a small bowl. Set aside.
Heat a wok until hot. Add the oil, then add the beef and stir-fry it until browned. Remove from the pan using a slotted spoon and set aside.
Add more oil to the wok if necessary (I did not need more oil), then toss in the onion and stir-fry for 4 minutes. Add the carrots and the beans (or broccoli) and stir fry for 2 minutes. (I gave it closer to 4 or 5 because of the broccoli), then add the garlic and ginger and stir-fry for 1 minute longer.
Pour in the hoisin sauce mixture, stir in the beef, and cook for 3 minutes. Serve immediately.