Step 1

Combine water, kombu, and bonito flakes in a large saucepan and bring to a boil over high heat. Reduce to a bare simmer and cook for 5 minutes. Remove from heat, let cool for 5 minutes, then strain through a fine-mesh strainer. Discard solids.

Step 2

Return broth to a medium saucepan and set over low heat to keep warm, but not boiling. Place a fine mesh strainer in the broth and add the miso paste to the strainer. Use the back of a spoon to press the paste through the strainer into the broth, Discard and large grains that don't pass through.

Step 3

Add tofu, wakame, mushrooms, and cockles (if using), and allow to cook without boiling until ingredients are warm and wakame has re-hydrated, about five minutes. Garnish with scallions (if using) and serve immediately.