Mefun: Hokkaido Salt-Cured Salmon Kidney in Ginger Soy

Steps

1. 1Take out the kidney

   Gut the salmon soon after you buy it. Parasites in the organs move into the flesh after the fish dies, so the guts should not sit inside. Open the belly, remove the organs, and find the dark-red strip running along the inside of the backbone. Scrape it out with the tip of a knife or a metal spoon, working from one end to the other so it comes away in long pieces. You are done when the backbone shows clean bone with no red left along it.

2. 2Freeze before anything else

   Lay the kidney flat in a zip-top bag, press out the air and seal it. Freeze it at -4°F (-20°C) or colder for at least 24 hours. Thaw it in the refrigerator, never on the counter. It is ready for the next step when it is soft all the way through and still cold.

   Raw salmon and parasites

   Salmon can carry anisakis larvae, and salt, soy sauce, vinegar and wasabi do not kill them. Only freezing at -4°F (-20°C) or colder for 24 hours or more makes this dish safer, so check with a freezer thermometer that your freezer gets that cold. If it doesn't, buy a jar instead. Keep the fish cold and take out the kidney the day you buy it. Use a clean board and tools kept apart from other food, and wash your hands and containers well. People who are pregnant, elderly, very young or have weakened immunity should skip homemade mefun and choose a fully cooked dish instead.

3. 3Draw out the blood in ice water

   Fill a bowl with ice water and slip in the thawed kidney. Leave it for several hours in a cool spot, adding ice as it melts so the water stays very cold. Swirl it gently with chopsticks now and then without tearing the strips.

4. 4Bury it in salt overnight

   Rinse the kidney gently and coat it heavily with coarse salt. Put it in a lidded container and add more salt on top until no red shows. Cover and refrigerate overnight, up to a full day. It is ready when the salt is stained with blood and nothing slides out when you turn the container upside down.

   The upside-down test

   Turning the container over is your cue. If the salt and kidney shift or fall, they need more time, or more salt pressed over the top. When it holds, the kidney has given up its water and firmed enough to take the soy.

5. 5Rinse off the salt and soak in ice water

   Wash the salt away under cold running water. Put the kidney in fresh ice water for 30 minutes to 1 hour, then pour off the water and start again with new ice water. Do this about three times. The kidney is ready for the soy when it is firm and darker than before.

   Setting the saltiness

   The salt level is set here. A longer soak in each round gives you milder mefun, and a shorter one leaves it saltier for drinking food. If the first batch is too salty, soak the next one longer.

6. 6Pack it with ginger and soy

   Pat the kidney dry with paper towels, pressing lightly so no water dilutes the soy. Pack the strips whole into a clean jar or container and scatter in the chopped ginger, ¼ knob for each fish. Pour in soy sauce until every piece is completely covered. You are done when no kidney rises above the surface of the soy.

7. 7Steep in the refrigerator

   Close the jar and refrigerate it for 2 to 3 days. Leave the strips whole the entire time. Keep the jar cold and use a clean utensil whenever you open it. The mefun is ready when it has turned a deep, glossy reddish-brown all the way through and smells of soy and ginger.

8. 8Chop just before eating

   Take out only what you will eat and return the jar to the refrigerator. Chop the kidney finely with the tips of your chopsticks, right before it goes on the table. Spoon a little over a bowl of freshly steamed rice, or set it out in a small dish with sake or shochu. It is right when the pieces are soft, glossy and fine enough to cling to the rice.

   Cut at the table, not before

   If you cut the kidney before steeping it, a bloody smell seeps out of the cut surfaces into the soy. Kept whole until serving, it stays clean-tasting.