Funazushi — Ancient Fermented Carp of Lake Biwa

Ingredients

• 2–4 Nigorobuna crucian carp (female, roe-bearing), wild-caught from Lake Biwa only; cleaned and gutted through the gills, scales intact
• 500 g per kg of fish coarse non-iodised salt, divided: first salting and rice-packing stages
• 600 g per kg of fish short-grain white rice, cooked, cooled to room temperature
• 20 g per kg of cooked rice salt, mixed through cooked rice before packing
• Equipment
• 1 large ceramic or wooden fermentation crock, lidded, capable of holding the fish fully submerged under weight
• 5–10 kg clean heavy stones or equivalent press weights, for consistent, sustained pressure throughout fermentation

Method

1. 1
   In spring, source female Nigorobuna carp carrying roe. Clean each fish through the gill cavity, removing viscera without breaking the roe sac; leave scales intact. Pack the body cavity and gill cavity densely with coarse salt. Layer the fish in the fermentation crock, covering each layer thoroughly with salt. Cover with a weighted lid and leave in a cool, dark place for several months (typically until early summer). The fish are ready for the next stage when the flesh has firmed noticeably under finger pressure and a clean brine has formed around the fish.
2. 2
   Remove the fish from the salt cure. Rinse each fish thoroughly under cold water, clearing all surface salt from the scales and cavities. Pat dry. This is the hinge between the salt stage and the rice fermentation: the fish must be clean of excess salt, which would inhibit the lactic acid bacteria activity in the next stage.
3. 3
   Mix the cooled cooked rice with its measured salt. This is where the dish lives or dies. Pack the rice into every cavity of each fish — gill cavity, body cavity, every internal space — until no air pocket remains. Lay a dense bed of salted rice in the bottom of the crock, place the fish on it, and pack salted rice completely around and between each fish, excluding all air from every surface. Any gap that admits air invites oxidative spoilage rather than lactic reduction. The packed crock should show no fish surface exposed to open space.
4. 4
   Place a fitted lid or plate directly onto the packed rice surface and load the heavy stones on top. The weight must be consistent and heavy throughout fermentation — pressure is integral to the acidification environment, not merely a physical seal. Store in a cool, dark place. Monitor periodically: if brine rises above the lid, remove a small quantity; if the surface appears dry, it may be pressed further. Fermentation continues for one to three years. At one year, the flesh will be semi-translucent and deeply sour; at three years, the flavour complexity increases substantially.
5. 5
   When fermentation is complete, remove the fish. The flesh should be semi-translucent, neither soft nor firm in a familiar sense — something between cooked and preserved. The roe, if present, will be dense and concentrated. Slice the fish into the thinnest possible cross-sections. Serve alongside portions of the fermentation rice (naka no meshi), which provides a sour, umami-rich counterpoint.