This tropical species is a distant relative of oyster mushrooms, it is often mistakenly called Pleurotus sajor-caju. Lentinus sajor caju Grows with Large leaf privet (ligustrum lucidum) in some of our lower sub tropical valleys. It is probably getting less common because privet is considered a weed and is targeted by landcare groups for eradication, so many areas of privet have been destroyed, however like most weeds it can still be found in abundance in places. I think the Coffs coast is getting near to the southern edge of the lentinus sajor caju range, the mushroom is probably more abundant further north. Having said that I know of at least one spot where they grow in abundance locally. Fruiting in the warm weather after rain on dead wood. I am not sure if they will fruit on other wood besides privet but it is likely. It is sometimes hard to ID a dead tree!
These fungi taste pretty good, similar to regular oysters tho they become quite tough and leathery soon after they form so they are best picked while in the ‘button’ stage. My main concern with these mushrooms is that they may bio-accumulate herbicides like glyphosate if they are growing on a poisoned tree. This is often the case because Landcare groups target privet. Bio-accumulation is a process where the mushroom mycelium concentrates a toxin from the substrate in the fruit body. I really don’t know how much of a problem this is and its unlikely that any studies have been done. Some mushrooms are able to break down the toxins rather then concentrating them.
The persistent ring on the smooth stem, their abundance on dead private and the vase shape that often holds water are helpful things to look for when IDing these mushrooms, one other thing to look for with a microscope or magnifying glass is the serrated edge of the gill. This fungi can dry out in situ and remain on the log for months after fruiting. The leatheryness of this fungi means they have a long shelf life in tropical climates where more fleshy fungi would spoil quickly. They are cultivated in parts of Asia. They grow in tropical Africa too and may be more widespread. I suspect they have been introduced to this part of Australia. They are more common in FNQ and could have hitched a ride down from there.