Konowata

Method

1. Dissolve 10 g of sea salt in 300 ml of ice-cold water in a bowl to make a seawater-strength brine and set it over ice. Rinse 3 live sea cucumbers under cold running water, rubbing the skin to remove grit. Everything from here should stay cold: the intestines spoil quickly at room temperature.
2. Lay each namako on a board with the mouth to your left and slit it open along the belly with the tip of a sharp knife. Ease out the coiled, pale-brown intestine in one long strand and drop it straight into the brine; discard the gonads, mouth and gut sac. You should have about 40 g of intestine in all. Reserve the body walls in cold salted water for namako sunomono.
3. Take each strand between thumb and forefinger and, working from one end to the other, squeeze the sand and dark contents out. Swirl the emptied strands gently in the brine, then pour off and replace the brine 4-5 times, until it stays clear and no grit settles at the bottom of the bowl. Handle lightly so the strands do not tear.