This recipe for chinese stir-fry beef with three vegetables features an interesting contrast of textures and flavors that pleases both kids and adults. Marinated tender flank steak is stir-fried with bok choy, mushrooms, and red onion in a flavorful dark soy sauce with rice wine or sherry sauce. Not only is this delicious but, since the number three symbolizes prosperity in the chinese culture (and there are 3 vegetables), it's considered a lucky dish. If you are not familiar with how to stir-fry beef, before you start preparing this dish, you may want to arm yourself with some pointers, such as freezing the meat for easy slicing.