Photo: Lamacchiacosta (CC BY-SA 4.0) via Wikimedia Commons · source
Florence's street sandwich: tripe (lampredotto) or beef simmered for hours in a vegetable broth, chopped onto a crusty roll whose top is dipped in the broth, with green sauce and chili oil. At home, beef brisket gives you Rome's allesso the same way.
A handful of parsley stems, 1 bay leaf, 1 tsp black peppercorns
Salt
6 crusty round rolls (semelle or kaiser)
For the salsa verde: 1 big bunch flat-leaf parsley, 1 tbsp capers, 2 anchovy fillets, 1 small clove garlic, 1 hard-boiled egg yolk, 1 slice white bread soaked in 1 tbsp vinegar, 100 ml (scant 1/2 cup) olive oil
For the chili oil: 4 tbsp olive oil, 1 tsp red pepper flakes, warmed together and cooled
How to make it
Simmer (2 1/2 to 3 hr): Put the meat in a pot with the vegetables, herbs and peppercorns, cover with cold water by 5 cm and bring slowly to a simmer. Skim. Add 1 tbsp salt and simmer very gently until a knife slides in easily: lampredotto 2 1/2 hours, brisket about 3. It should never boil hard.
Make the salsa verde (10 min): Squeeze the bread, then chop it fine with the parsley leaves, capers, anchovy, garlic and yolk (or pulse in a food processor). Stir in the oil and a pinch of salt; it should be loose and bright.
Chop (5 min): Lift the meat onto a board and chop roughly into bite-size pieces. Salt and pepper it generously.
Dip the roll (1 min): Cut the rolls through. Dip the cut side of the top half in the hot broth for 2 seconds (bagnato).
Build: Pile the hot meat on the bottom half, spoon on salsa verde and a little chili oil, and close. Eat right away, over the paper, with a glass of red.
Tips
The broth is superb soup the next day with pastina.
Ask the butcher for lampredotto already cleaned and blanched.