Northern ceviche — Trujillo, seasonal version

Boil the sweet potato.Put the peeled 500 g sweet potato pieces in a saucepan with 1300 ml water. Bring to a simmer, then cook for 23 minutes. Drain and spread the pieces on a clean shallow tray. The sweet potato yields to a knife but retains neat pieces on the plate. Keep the cooked sides separate from raw fish during their later cooling period.

Cook yuca and choclo.In another saucepan, add exactly 1300 ml water and the 300 g peeled yuca. Simmer for 25 minutes; add the 340 g choclo kernels for the final 12 minutes. Drain into another clean shallow tray. Remove any remaining tough yuca fibres. The yuca can be pierced through easily and the choclo kernels are tender rather than chalky. Cassava must be peeled and thoroughly cooked; never sample raw yuca.

Cool the cooked sides safely.Spread the cooked 500 g sweet potato, 340 g choclo and 300 g yuca in shallow clean containers and refrigerate for 60 minutes, keeping uncooked fish separately cold. The containers must not be left on the counter to cool. The cooked sides have cooled through and are no longer warm enough to heat the raw-fish plate. Allow 60 minutes passive chilling for this step. Keep at 4 °C or below once chilled.

Prepare the cold flavourings.With a clean vegetable board, cut 180 g red onion into fine plumes; finely chop 15 g ají limo and 20 g coriander, and grate 8 g garlic. Put each in a separate cold bowl. The onion slices are thin enough to bend, and the chili and coriander are finely cut without being mashed. Allow 12 minutes for this step.

Squeeze and chill the lime.Gently squeeze enough clean limes for exactly 170 ml strained juice, avoiding scraping the bitter pith. Chill the juice while preparing the fish. The juice is free of pips and large pulp fragments. Allow 4 minutes for this step.

Dice and hold the fish cold.Using a sanitized raw-seafood board and knife, cut the 700 g boneless fish into 2 cm cubes. Put it in a cold bowl over ice at or below 4 °C. Do not leave the fish on a warm worktop. The fish pieces are cleanly cut, firm and cold to the touch, with no strong or sour smell. Allow 7 minutes for this step. Previously frozen/appropriately parasite-controlled fish is still raw and can contain harmful microbes.

Dress the ceviche just before eating.Toss the chilled fish with all 5 g salt and 8 g grated garlic, then pour over exactly 170 ml lime juice. Fold in 15 g ají limo, 180 g red onion and 20 g coriander. Mix gently for 2 minutes only; do not leave it to stand in the citrus. The fish is evenly dressed and moist, with onion and coriander distributed rather than crushed. Lime juice does not cook, pasteurize or make raw fish safe.

Plate and serve immediately.Arrange the cooled sweet potato and choclo and fully cooked yuca beside the ceviche and divide among 4 adult servings. Pass 60 g dry cancha in a separate bowl. Eat at once; do not hold assembled ceviche for later. The fish remains cold, the root vegetables hold their shape, and crunchy sides stay dry. Allow 3 minutes for this step. This uncooked fish preparation is not appropriate for pregnant people, young children, older adults or immunocompromised people.