Fegato alla veneziana is Venice's classic liver preparation—thinly sliced calf's liver seared at high heat with a melting mass of slowly caramelized onions, finished with a splash of white wine or vinegar, and served over soft polenta. The dish is a study in contrasts: the quickly cooked liver (still pink inside) against the long, slow sweetness of the onions creates a balance that has made this one of the most imitated liver dishes in the world. The technique demands two separate cooking processes united at the last moment. The onions—thinly sliced, in enormous quantity (roughly equal weight to the liver)—are cooked very slowly in butter and olive oil for 30-40 minutes until they collapse into a golden-brown, jammy sweetness with no trace of their original sharpness. The liver is sliced paper-thin (3-4mm), patted dry, and seared in a blazing-hot pan for mere seconds per side—it should be caramelized on the exterior and rosy-pink within. The onions are combined with the liver, a splash of white wine vinegar or white wine is added and reduced, and the dish goes to table immediately. The liver must not be overcooked—the difference between pink and grey is measured in seconds, and grey liver is a failure of timing that cannot be rescued. The pairing with soft polenta is canonical—the creamy corn porridge absorbs the pan juices and provides a mild, sweet backdrop for the liver's iron-rich intensity and the onions' caramelized depth. Venetians are emphatic that the onions must be white onions from Chioggia, the fishing town at the southern end of the lagoon, whose sweetness is essential to the dish's balance.
Thinly sliced calf's liver, seared quickly at very high heat. Onions caramelized slowly for 30-40 minutes until jammy. Combine at the last moment. Deglaze with wine or vinegar. Liver must be pink inside. Serve immediately over soft polenta.
Freeze the liver briefly (20 minutes) for easier thin slicing. The pan for searing must be smoking hot—don't crowd it. A splash of aged balsamic vinegar at the end adds Venetian depth. The onions can be cooked well in advance and reheated. Soft polenta should be pourable—not stiff.
Overcooking the liver (must remain pink). Rushing the onion caramelization. Using too-thick liver slices. Not enough onions (should be equal weight to liver). Serving without polenta. Adding the liver too early to the onions.
Marcella Hazan, Essentials of Classic Italian Cooking; Tessa Kiros, Venezia