Beef with Chinese broccoli is a Cantonese favorite.  I really like Chinese broccoli, because when cooked right, the stems are "crunchy".  The sauce in this particular dish is heavy on the oyster sauce.  If you've every been for Cantonese dim sum, they will serve Chinese broccoli with oyster sauce as one of the dishes.  You can substitute this with regular broccoli, but if you are able to use Chinese broccoli, it's got more crunch.

Tips.

Beef.

The key to making this dish well is to use a good cut of beef.  The beef needs to be tender.  Otherwise, you will spend quite a bit of time, trying to chew the beef in order to swallow it.  I would recommend using either tri-tip or a sirloin.  Do not use stewing meat cuts as they are fairly tough.

Chinese broccoli.

Unlike regular broccoli, Chinese broccoli is a leafy vegetable with thick stalks, rich in nutrients and good source of Vitamin C, Vitamin K and Vitamin A.  In my Chinese stir frying basics, one of my tips is to make sure that all your veggies in the stir fry are fairly uniformly cut.  This allows for even cooking.  For the Chinese broccoli, separate the stalks from the leaves. Unlike regular broccoli, Chinese broccoli have very thick stalks.  Usually these stalks, although thick, are not tough when properly cooked.  Sometimes, especially during the summer when the weather is hot, these stalks will tend to have a thick outer layer that is tough and stringy.  If you happen to purchase a bunch with thick stringy stalks, use a peeler and peel the outer layer.  You can then cut the stalks at a diagonal so that all the stalks are fairly uniform in size.