The panino catanese is Catania asserting that the eastern Sicilian street has its own meat, and that meat is most often horse. Carne di cavallo, grilled over coals at a stall and packed into bread, is the dish the city is known for, a lean, faintly sweet, mineral red meat with none of the fat of beef, treated fast over fire and eaten where it is cooked. Around it sits the local sausage, the salsiccia catanese spiced and coiled, and the same vat of fried things Sicily puts in everything. The defining fact is the protein and the fire: this is not a cured-meat panino built at a counter but a grill panino, the bread there to carry something hot and just off the coals.
The craft is the fire and the dressing. Horse is lean enough to dry if it is overcooked, so it is grilled hard and fast for char and then pulled while it is still giving, sliced or left in pieces and packed into a soft roll while the heat is still in it. Salsiccia catanese, fattier and aromatic with fennel and chilli, is split and grilled so the fat renders into the crumb. The bread is plain and soft on purpose, a sesame roll close to the Palermo vastedda, because everything assertive has happened on the grill and the bread's only job is to hold it. Salt, lemon, sometimes a sharp tomato or grilled onion, are added at the stall to cut the iron of the meat, and the thing is eaten standing before the fat sets.
The variations stay on the same street and the same coals: the horse-meat build against the salsiccia one, the version that tucks in the fried crocchè and panelle the city sells alongside, the one finished with the local tomato or grilled onion. Each of those is a different Catanese thing off the same grill, and each deserves its own article rather than being crowded in here.