Sup Miso Kerang Jepang

Bahan-bahan (2 porsi)

• ½ lb Manila clams
• 2 cups water
• 1 piece kombu (dried kelp) ((0.2 oz, 5 g; 2 x 2 inches, 5 x 5 cm per piece))
• 2 Tbsp miso ((I use koji miso or awase miso))
• 1 g reen onion/scallion ((finely chopped))