sugar crystals, all of it, whether from fondant, syrup or granulated honey, even the white goo. i think the flash may have also affected the 'coloring' of these cells to make them appear white, unless it is fondant that is melting and dripping out. if you blow the photo up, there are some cells with 'honey' or 'liquid' dripping out, you can also see crystals in the bottoms of these cells through the honey/liquid.
the mouse nest zweef, sad that happened to you, they are destructive little buggers.