Shijimi Misoshiru (しじみの味噌汁, freshwater clam miso soup)

Ingredients

Equipment Needed

• •Shallow bowl or tray for sunanuki (sand purging)
• •Medium pot
• •Miso koshi (miso strainer), or a ladle and chopsticks
• •Small sieve for lifting the clams from the purging water

Instructions

1. 1

   Purge the clams

   Discard any shijimi with cracked shells or a sour smell. Mix 1 liter cold water with 10g sea salt in a shallow bowl, then add the clams in one layer and cover loosely. Keep them cool and dark for 2 to 3 hours. Shijimi are freshwater to brackish clams, so this mild 1 percent salt bath is enough; the stronger seawater bath used for asari is not the one we want here.

   Shallow water and darkness keep the clams settled enough to release sand. This is the one detail that decides whether the soup tastes clean.
2. 2

   Rinse and sort

   Lift the clams out of the purging water with your hands or a small sieve, leaving the grit behind. Don't pour the water through them. Rub the shells together under cold running water until they feel clean and no grit catches under your fingers. If any shell gapes and will not close when tapped, discard it.

3. 3

   Start the broth

   Put the cleaned shijimi, 4 cups cold water, the optional konbu, and the optional sake into a medium pot. Bring it up slowly over medium-low heat. If using konbu, pull it out when the water trembles and small bubbles climb the sides, before the boil arrives. Boiled konbu can turn the broth faintly bitter and slick, and this little soup has no heavy seasoning to hide that mistake.

   Starting cold lets the clam liquor move into the water before the meat tightens. The clams are the dashi here; the konbu is only a quiet helper.
4. 4

   Open and skim

   When the first shells open, lower the heat so the broth barely moves. Skim off the pale scum as it gathers. Cook only until most shells have opened, usually 3 to 5 minutes, then discard any that stay shut. A hard boil knocks the shells around, clouds the broth, and makes the tiny clams tough.

5. 5

   Dissolve the miso

   Turn off the heat. Put 3 tablespoons miso into a miso koshi, or into a ladle, and loosen it with hot broth before stirring it back into the pot. Taste, then add more miso only if the broth asks for it. Never boil miso once it is in the soup; boiling drives off its fragrance and leaves a rough salt edge.

   If the soup tastes thin, next time use more shijimi or a little less water. More miso gives salt before it gives depth.
6. 6

   Serve at once

   Ladle the clams and broth into warm bowls and finish with a few thin scallion rings or one small sprig of mitsuba. Serve at once, while the surface is glossy and the clam fragrance is still clear. The clams are small, but they are not decoration; pick them from the shells as you drink the soup.

Chef Tips

• •Ask the fishmonger when the shijimi came in and whether they have already been purged. The shells should be moist, closed, and clean-smelling. If they are dry, cracked, or sour, change the dish. Nothing hidden.
• •Don't use powdered dashi here. There is a difference between a sensible stand-in and salting over the point of the bowl. The little shells make the stock themselves, and that is the honmono of this soup.
• •Aka miso gives a deeper, earthier bowl, while awase miso gives a gentler one. Either is proper. White miso is usually too sweet for shijimi unless the clams are very strong.
• •If you cannot find shijimi, asari or Manila clams will make a good clam miso soup, but it is a different dish. Say so plainly and cook it with respect.

Advance Preparation

• •Purge the shijimi the day you buy them if you can. After purging and rinsing, keep them in the refrigerator in a covered bowl lined with a damp cloth for up to 24 hours; do not leave them submerged overnight.
• •For a weeknight bowl, purge and rinse the clams, then freeze them flat in a bag for up to one month. Cook them from frozen in cold water, adding a minute or two to the simmer.
• •Finished miso soup does not like waiting. If you must reheat it, warm it gently to just below a simmer and add fresh garnish at the table.

Frequently Asked Questions

Nutrition Information

1 serving (about 265g)