This can be worn around the neck as a cowl but the cowl I made will fit snugly around my shoulders.
Gauge is not critical for this garment as the stitch used and the construction has a lot of stretch anyway. My piece of Brioche was about 81cm long (unstretched) before doing the cable.
I did not block my cowl!

Techniques used:
Judy’s Magic Cast On (or your favourite provisional cast-on) - Link to YouTube Video is here
Brioche stitch
Cabling without a cable needle (not critical if this freaks you out but here’s a helpful video if you’d like to try!)