Castelvetrano olives are named after an eponymous town in Sicily, where they’re grown both for pressing into olive oil and simply for snacking (you might find one in your next martini, too!). Unlike the typical green olive you’d find in a salad or entrée, Castelvetranos’ mild flavor comes from being harvested at a younger stage, and because they’re typically packed in a brine that has less salt than other jarred olives. The flavor of these bright green gems leans subtly sweet and buttery, with a mellow tang. When compared to the ubiquitous little green olive in a can, the Castelvetrano is larger and substantially meatier, meaning it truly is an olive you can sink your teeth into.
All of these attributes make for an olive that is simply perfect for baking bread. The reduced salt content means less interference with your intended flavor profile (much like a baker who prefers to use unsalted butter so the salt content is completely under their control) and the thick, meaty olive flesh makes for a dramatic presentation in the loaf’s cross sections—and a substantial bite with every slice of bread.