After de-gritting the clams, rub the shells together to remove any dirt.
Combine the water and clams in a pot, and bring to a boil over high heat. Reduce to low-medium heat, and simmer while skimming any scum from the surface.
Reduce the heat to low once the clams open up, then add the miso. Sprinkle in some green onion or scallions to taste.
Story Behind this Recipe
I learned this recipe from my mother.
When de-gritting the clams, put them in water for about 1 hour with 1% salt (skip this step for clams that have been de-gritted). You could use kombu dashi soup stock or add kombu to the soup, but it's very delicious without it. Too much water will eliminate the taste of the clam, so be careful not to use too much.