Step 1

Use a slightly damp cloth to gently wipe the surface of shiitake mushrooms and kombu.

Step 2

To make the broth: in a large bowl, combine water, shiitake mushrooms, and kombu. Refrigerate and let soak overnight.

Step 3

Whisk together miso, soy sauce, and 3 tbsp of the broth in a small bowl.

Step 4

Remove the soaked shiitake mushrooms from the broth, gently squeeze out the excess liquid, and slice.

Step 5

Strain the remaining broth with a fine-mesh strainer into a large pot and add kombu back into the broth. Add leek, carrot, shiitake, and shimeji mushrooms.

Step 6

Bring to a boil over medium-high heat. Discard kombu to prevent the soup from becoming slimy.

Step 7

Add mirin, aburaage, and udon noodles. Cook for 8 mins, stirring occasionally to prevent sticking. Reduce the heat to low if necessary to maintain the gentle simmer.

Step 8

Stir in miso mixture. Add salt to taste. Place bok choy on top and cover to cook for 2 mins until noodles are tender.

Step 9

Serve the pot as is with serving bowls to share on the table, which is an authentic way to serve in Japan, or divide into serving bowls.

Step 10

Top with black sesame seeds and enjoy.