The Maremma, southern Tuscany and adjacent Lazio. The soup of the field workers, charcoal burners, and shepherds who had fire, water, and whatever aromatics they could carry. Documented in Artusi's 1891 work as a regional Tuscan tradition.
Acquacotta — 'cooked water' — is the ancient soup of the Maremma, made by the butteri (Maremma cowboys) and charcoal workers (carbonai) in the field from whatever was available: onion, wild herbs, tomatoes, and stale bread, cooked in water with olive oil and finished with an egg poached in the soup. It is one of the defining examples of cucina povera philosophy: a name that proclaims its poverty ('cooked water') while the technique coaxes extraordinary flavour from near-nothing.
Long-cooked onion creates a sweet, concentrated depth that makes the soup taste like a labour-intensive stock — when in fact it is only caramelised onion in water. The poached egg richness, the bread starch, and the pepper-and-grass of the finishing olive oil complete a dish that tastes far more complex than its ingredients suggest.
The base is a very slow-cooked onion in olive oil — 30-40 minutes until completely soft and deeply golden. Tomato (or dried mushrooms in the winter version) is added. Water is added and simmered 20 minutes. The flavour concentrates the way a broth would, because the slow-cooked onion releases sugars and the olive oil carries them. Stale pane sciocco is placed in the bowl, the soup poured over, and the final step is either an egg poached directly in the soup pot or cracked into the bowl and left to set in the hot soup. Pecorino and olive oil at the table.
The egg version (the classic) should have a barely set white and runny yolk — lower the heat, crack the egg directly into the simmering soup, cover for 3 minutes. The mushroom variant (with dried porcini and their soaking water added to the onion base) is a winter richer version. Acquacotta demonstrates better than almost any dish that ingredient quality and technique — not complexity — determine flavour.
Rushing the onion — the depth of acquacotta comes entirely from the long-caramelised onion. Using too much water — the soup should be concentrated, not watery. Fresh bread instead of stale — the bread should absorb soup, not create a paste. Not finishing with olive oil and pecorino — these are the dish's finishing flavours.
Elizabeth David, Italian Food; Pellegrino Artusi, La Scienza in Cucina