Florence, Tuscany. The trippai of Florence have documented history going back to the 14th century. The city's butchering tradition — and the Florentine culture of eating the whole animal — made lampredotto the defining street food of the city.
Lampredotto is the fourth stomach of the cow (the abomasum — the true digestive stomach, as opposed to the other three rumen chambers) slow-cooked in a broth of onion, celery, carrot, and tomato until tender, then sliced thin and served in a semolina roll (semellino or bun) dipped in the cooking broth, dressed with salsa verde and hot sauce (salsa piccante). It is the street food of Florence — sold from trippai (tripe carts) in the San Lorenzo market and throughout the city. Nothing marks Florentine identity more precisely.
Lampredotto has a deep, intensely savoury, gelatinous character — the fourth stomach has more fat and a stronger flavour than the other tripe sections. The broth dipping enriches the bread; the salsa verde cuts through the richness with parsley and caper acidity; the hot sauce adds heat. This is offal eating at its most honest and satisfying.
Lampredotto requires long simmering — 2-2.5 hours at a gentle simmer in aromatic broth — until a knife slides through without resistance. The broth is reserved; the tripe is sliced on a cutting board. The semellino roll is split, the bottom half dipped briefly in the hot broth (the 'bagno' — essential), filled with the hot sliced lampredotto, dressed with salsa verde (parsley, capers, anchovies, garlic) and hot sauce. The bread becomes soft from the broth but should not be soggy. Eaten standing at the lampredotto cart.
The quality of the cooking broth determines the lampredotto flavour — if the broth doesn't taste like a good bouillon, neither will the lampredotto. The hot sauce used in Florence is a simple Italian red chilli sauce — not a Mexican or Asian hot sauce; the heat should be simple and direct. Lampredotto has a slightly gelatinous, very tender texture and a deep, umami-rich flavour — it is one of the most satisfying offal preparations in Italy.
Under-cooking — lampredotto must be completely tender throughout. Not dipping the bread — the 'bagno' is essential; it seasons the bread and softens it to the right texture for eating with the tender tripe. Omitting the salsa verde — the green sauce's acidity is the essential counterpoint to the rich, gelatinous tripe. Refrigerating sliced lampredotto — it tightens; serve immediately after slicing.
Elizabeth David, Italian Food; Faith Willinger, Eating in Italy