Very quickly blanch the Chinese broccoli in salted water. Alternative: steam until just cooked.
Saute shiitake mushrooms until golden and aromatic with garlic. Then, add in oyster sauce mixture.
Cook on low heat, stirring constantly until sauce thickens and lightly bubbling. About 2 minutes.
Add the Chinese broccoli into the pan, mixing for about 1 minute. Ensure even coating of sauce.