Lard bubbles in shallow vats. Outside, the sun is punishingly hot. In a narrow shop facing the port, the Favata family scrambles to keep up with the lunch crowd. Domenico and Gieuseppe slice offal to order. Gaetano pulls meat off drying hooks. Rosario shouts the orders as they come in. Everyone's here for what's in those gurgling vats, for the only thing served here: pani ca' meusa, the glorious grease bomb, classic street snack of this city, consisting of a soft sesame roll hollowed out and piled with a bounty of meusa (spleen) and lung, sometimes trachea. The sandwich, whose fame has not spread to mainland Italy, traces its origins to the 15th century, when the city's butchers were paid for their services in scraps by Kosher-keeping customers.