Miso Soup with Clams

Ingredients

• 1 pound small asari, cockles, or littleneck clams
• Cold water
• Kosher salt
• 2/3 ounce dried kombu, rinsed in cold water
• 3 tablespoons mild miso, such as shiro miso
• 1 tablespoon dark miso, such as aka miso
• Mitsuba or watercress leaves, for garnish

Directions

1. Wash the clams well under cold running water. Put cold water in a large bowl, stir in kosher salt until it tastes seawater-salty, about 3% salt by weight, then add the clams. Leave them for 30 minutes, then scoop the clams out and pour off the water. Clean the bowl, then do the same purging process again until the bottom of the bowl stays free of sand or grit, usually between 1 and 3 times.
2. In a medium saucepan, add the kombu, clams, and 3 1/2 cups (830ml) cold water. Warm everything over medium heat until it reaches the gentlest simmer, about 8 minutes. The moment that simmer starts, take out the kombu and discard it, or save it for another use.
3. Let the pot keep simmering, and as each clam opens, move it with tongs to a large heatproof bowl. Once every clam has opened, skim the foam from the top of the dashi. Pour the dashi into a clean medium saucepan and hold it warm over low heat.
4. Whisk both misos in a small bowl with just enough dashi to loosen them into a thin paste. Take the saucepan off the heat, then whisk the miso mixture into the dashi.
5. Arrange the clams in warm bowls, then ladle the miso soup over the top. Finish with mitsuba or watercress leaves and serve right away.