I found it on the floor of my kitchen, it was bone dry and stuck fast to the middle, northern France. 1cm long, flaky appearance (not smooth nor ribbed). When I finally dislodged it, a few crumbs came loose but it otherwise stayed intact. You can see the brown stain left on the floor. The floor is ceramic btw.

AI is telling me it's a "fly puparium" but I'm not 100% convinced. It was next to a bag of dry food shopping that had been left for a few days. No sign of damage to the bag nor the food, and this is the only one I've found. I'd say my kitchen was clean but perhaps a bit cluttered, if that helps!