Have you heard of a “duck”?

Has anyone out there heard of a duck? This is a bready (brioche-y?) finger or rectangle, with a creamy lemony filling or glaze. I only remember it vaguely from a single tasting in my youth. It was a favourite of my dad’s, however, and I’d love to find one for him.

 

ceci n'est pas un canard
ceci n’est pas un canard

One slight problem, “duck” might be a family name for this confection, and not the official one at all!!! Please help if you can!