Brodetto Marchigiano di Ancona — Adriatic Multi-Fish Soup with Vinegar

Ingredients

• 1 large onion, finely sliced
• 60 ml extra-virgin olive oil
• 3–4 tbsp crushed tomato, enough for colour, not a tomato sauce
• 80–100 ml white wine vinegar, good-quality wine vinegar; the defining element
• Fish — added in order of robustness
• 300 g cuttlefish (seppie), cleaned, cut into pieces
• 250 g scorpion fish (scorfano), cleaned and scaled
• 250 g gurnard (capone), cleaned and scaled
• 200 g weever (tracina), cleaned
• 200 g skate (razza), cut into portions
• 200 g red mullet or bream, cleaned and scaled
• Shellfish — added last
• 200 g clams (vongole), scrubbed and purged
• 200 g mussels (cozze), scrubbed and debearded
• 200 g mantis shrimp (canocchie), whole; placed on top last
• sea salt, added at the end only
• To serve
• 4 thick slices Marchigiani bread, toasted until deeply golden

Method

1. 1
   In a heavy pot — terracotta is traditional — warm the olive oil over a moderate flame. Add the finely sliced onion and cook, stirring occasionally, until it is deeply golden and fully soft. The onion must not brown harshly; it should be sweet and yielding.
2. 2
   Add the crushed tomato — no more than three or four tablespoons. Stir it into the onion and allow it to cook briefly until the raw smell lifts and the oil takes on an orange tint. The tomato provides colour and body; it is not the base of a sauce.
3. 3
   Pour in the white wine vinegar in a generous splash. Allow it to cook into the base for a minute or two. This is where the dish lives or dies: the vinegar must be present in quantity sufficient to make the broth assertively and cleanly sharp throughout — a timid addition produces a generic fish soup, not brodetto all'anconetana.
4. 4
   Add the cuttlefish pieces. Reduce the heat to very low — the broth must barely tremble, never boil. Cook the cuttlefish for 15 to 20 minutes, until the pieces have lost their translucency and are just tender when pressed.
5. 5
   Add the firm whole fish: scorpion fish, gurnard, weever, and skate. Arrange them in the pot without disturbing the cuttlefish beneath. Maintain the gentlest possible simmer and cook for approximately 10 minutes, until the flesh at the thickest part of the fish just begins to yield to the side of a spoon.
6. 6
   Add the medium fish — mullet or bream. Again, settle them into the broth without stirring. Cook for 7 minutes. The flesh should be just opaque through to the bone; the skin intact and unbroken.
7. 7
   Add the clams and mussels. Place the mantis shrimp on top of everything as the final layer. Cover the pot and cook for 3 to 4 minutes. The moment the bivalves open and the mantis shrimp have just turned opaque — though still slightly undercooked — remove from the heat. Residual heat in the broth will complete them in the bowl.
8. 8
   Season with sea salt now, and only now. Place thick slices of toasted bread in the base of each bowl or alongside the pot. Serve directly from the pot at the table, each diner serving themselves.