A thumb-sized round of dough may carry the least glamorous origin story in the sweets cabinet: in Persia, bakers are said to have used small cakes to judge whether an oven's heat was ready for larger loaves. A probe, not dessert. If the account holds, the cookie began beside the furnace rather than the feast, where thermal mass and radiant heat, signaled by the Maillard reaction, turned a scrap of...More