I was in a local greengrocer's shop this morning and saw some of these vegetables so I asked if I could take a photo of them. The answer was Yes; I went back to the car to fetch the camera. It's a very pretty green with these little pimpled cones on them. (No, not the camera.)
I asked what it was but the lady in charge was only there for a few minutes to take the money while the owner was out so she couldn't help. However it was in a tray with 'proper' cauliflowers.
I've looked it up on Google Images where it's labelled as a Romanesco cauli, fractalish cauli and Italian cauli. It's said to have a mild, nutty taste somewhere between broccoli and cauliflower - a wonderful partner to pasta. (What does 'fractalish' mean? Something to do with 'broken'?)
But another post says it's not a cauliflower but a Romanesque broccoli...it's apparently linked to Fibonacci numbers but then, I'm not into numbers...
Seems as if yer pays yer money and takes yer choice.