Butterfish. I just looked it up in The Australian Seafood Handbook - Domestic Species (eds. Yearsley, Last and Ward; updated version 2001; published by CSIRO Marine Research and the Fisheries Research and Development Corporation.)
It's a great book, but I'm none the wiser*.
Butterfish has also been known as Dory, John Dory, Morwong, Old Maid and Scat; while a number of other fish have in turn been known as Butterfish.
Whatever. The fish I bought was a succulent white-fleshed cutlet.
I wok-fried onion, garlic, ginger, green beans, very finely julienned carrot and broccoli florets in peanut oil with a drop or two of sesame oil until crisp.
Set some jasmine rice to boil (absorption method, water to rice two to one, boil, switch off, let absorb).
Then, right when the vegetables and rice were almost ready, I pan-fried the fish simply in just a smear of peanut oil, adding a dash of nice soy and a squeeze of lemon when almost done. A few minutes either side.
Rice in a bowl, scatter greens over, fish over the greens, a sprinkle of sesame seeds, more lemon juice and soy.
Jasmine tea on the side.
*The book actually has a protein fingerprint identification appendix so it is possible to ascertain your fish.