Heat wok over high heat. Add the oil and the onion, and give it a few quick tosses. Next add in the beef and garlic, and cook, tossing continuously for about 5 minutes. Add the broccoli, tossing constantly for about another 5 minutes.
Add the water, lower the heat, and cover for an additional 5 minutes, until the meat is cooked through. Sprinkle the corn starch over the top, stir, and cook a few more minutes until the juices in the pan have thickened.
Serve over steamed rice.
Recipe by Webicurean at http://blog.webicurean.com/2014/02/01/quick-easy-broccoli-beef-stir-fry/