4cupsdashisee notes, chicken broth or vegetable broth (whatever is easiest and available to you)
In a medium pot, bring your dashi or broth to a boil over medium-high heat. As it is coming to a boil, rinse, scrub and debeard the clams and mussels and drain in a colander. When the broth is bubbling, stir in the miso paste and add the clams and mussels. Cover with a lid and let it cook for about 2 minutes, or until the clams and mussels have opened. Discard any that remain closed.
Ladle the soup into bowls and garnish with scallions. Enjoy immediately.
Dashi is a Japanese stock or broth and is the traditional base for miso soup. Learn how to make dashi stock from Just One Cookbook. If you like, you can also substitute chicken or vegetable stock – it is just as good!