I was inspired by the fold-back cuffs on my sons' snowsuits when they were toddlers. The end of the sleeve had a second layer which folded over the hands to keep them warm, or folded back if you wanted their hands free. However, those had quite blunt ends and unless the sleeve was long or the fist was bunched, there didn't seem to be quite enough room.
Using short rows I have made the fold-back flap shaped to allow enough room for the longer fingers in the middle but without making things draughty for the little finger at the end! Clever, huh?!
The afterthought thumb is closed, but you could leave the end open if you prefer.
The photos were taken on a cross-channel ferry between Dunkerque and Dover. It was a lovely calm crossing, sunny but chilly, and I was actually glad I'd brought the mitts along for photographing because it meant I could stay outside and enjoy the sunshine without getting cold fingers.