The Four Roman Pastas

Rome's four canonical pastas are really one recipe evolving, and the city can draw you the family tree. It begins in the Apennine pastures with gricia: guanciale — cured pork jowl, never bacon — rendered crisp, its fat emulsified with pecorino romano and pasta water. Shepherd's food: three ingredients, no waste, complete.

Subtract the guanciale and grind in pepper and you have cacio e pepe, the minimalist's vertigo — nothing but cheese, pepper and starch-water, and therefore nearly impossible to make well. Add tomato to gricia instead and you have amatriciana, named for the mountain town of Amatrice, defended by statute: onion and garlic are both controversies, bucatini the traditional vehicle.

The youngest sibling is the famous one. Carbonara — guanciale, egg yolk, pecorino, pepper — appears in print only after the Second World War, and Rome shrugs at the theories (coal-burners' lunch? American rations of eggs and bacon meeting Roman technique?). The eggs must never scramble; the sauce is a custard achieved off the flame, gold as everything else on this trip.

On Day 8 at Trattoria Monti the menu leans to Le Marche, but the lineage is all around you every Roman evening — and the only rule that matters: cream in carbonara is grounds for deportation.