Florence's iconic tripe sandwich from street carts — abomasum in green sauce on crusty bread. This high protein mediterranean street food is a lean, carnivore tradition unique to the Tuscan capital.
Rinse the beef abomasum tripe under cold water, then place it in a large pot with the onion, carrot, and celery. Add water to cover, bring just to a boil, then reduce to a gentle simmer.
Skim any foam from the surface, add 2 tsp kosher salt, and simmer partially covered over low heat for about 1.5 to 2 hours until the tripe becomes very tender.
While the tripe cooks, make salsa verde: In a food processor, pulse the fresh parsley, capers, garlic cloves, red wine vinegar, and half of the olive oil. Blend until a coarse green sauce forms, then stream in remaining olive oil. Season with pepper to taste.
Once tender, remove the tripe and slice it thinly across the grain. Taste and season with extra salt if needed.
Slice the sandwich rolls, briefly steam or toast open-side down on a dry skillet, and mound hot sliced tripe inside each roll. Spoon salsa verde generously over the meat and serve immediately.