Last fall, an aberrant chocolate chip cookie turned up in my Instagram feed. As wide as a salad plate and flat as a flounder, it appeared thin, but it was somehow layered with slabs of chocolate. Oddest of all, it was ringed, like a tree trunk.
But soon, the rippled cookie appeared again: as a one-off from a bread blog, then in 42burners, the Instagram account of Martha Stewart's. It showed up, insistently, as baker/photographers like Ruth Tam kept posting it, crowing about the crispiness of the ridges and the softness of the centers.