Ayu Uruka (Salt-Cured Sweetfish Paste)

Keep 500g whole ayu at 4°C or below after purchase and prepare it the same day.

Wash and sanitize hands, knife, board, mortar, and a lidded glass container with boiling water or food-safe sanitizer, then dry completely.

Scrape away the scales lightly and remove the heads.

Open the bellies, remove all intestines, rinse very briefly in cold water, and dry the cavities and surfaces completely with clean paper towel.

Discard the tails and cut the ayu through the small bones into 1cm pieces.

Weigh the cleaned fish; if it weighs less than 500g, reduce the salt to exactly 15 percent of that weight.

Put the cut fish and calculated salt in the mortar.

Press and grind for 10 to 15 minutes, until the salt is fully distributed and the fish becomes a soft, thick paste.

Pack the paste into the sanitized container a little at a time, pressing with a spatula to remove air pockets.

Level the surface, close the lid, and refrigerate immediately at 4°C or below.

Mature under refrigeration for 7 days, then use a clean spoon to serve about 15g per person.

Never return served uruka to the container, and keep the remainder at 4°C or below.