Pani câ meusa is the Palermo spleen roll, and it is defined by the pot of lard it is built around rather than by anything raw. Thin strips of veal spleen and lung are boiled, then finished in lard kept hot in a wide pan at the front of the stall. A soft, slightly sweet sesame roll, the vastedda, is split and loaded straight from that pan, the offal lifted dripping and packed in hot. The bread is plain on purpose: everything with character has already happened in the pot and the lard, and the roll exists only to carry a filling that is hot, fatty, and just cooked.
The craft is the lard temperature and the speed of the hand-off. The fat has to be hot enough to gloss the meat and keep it slack, but the roll is dipped only briefly, because a vastedda held too long in the lard turns to a sponge and collapses under the filling. The spleen has a distinct iron, almost mineral edge, and the lung adds a softer, spongier texture against it; the two are worked together so neither dominates. Salt and a hard squeeze of lemon are added to order at the counter, the lemon cutting the fat and the iron in equal measure. None of it survives a wait. The roll is handed over and eaten standing, within minutes, because a vastedda that has sat has gone slack and the lard has begun to set in the crumb.
The whole point of the sandwich is the fork that comes next. Ordered schietta, single, it is spleen, lung, and lemon only, lean and sharp. Ordered maritata, married, it gains shaved caciocavallo and a spoon of ricotta, the cheese rounding the iron and the fat carrying it longer. Those two are full preparations in their own right, as are the wider Palermo street family of panelle and crocchè rolls that run on the identical logic of a fryer or a pot poured into soft bread. Each deserves its own article rather than being crowded in here.