Step 1

Combine the dashi, usukuchi, mirin and kombu in a pot. Bring to a boil over high heat. Add the salt and katsuobushi, and immediately turn off the heat and strain into a nabe (hot pot) or medium saucepan. Add the udon and bring back to a boil. Reduce the heat and add the chicken and shitake mushrooms. Cook for 1 minute.

Step 2

Crack the egg into center of soup. Ladle the soup over the egg until it turns white. Remove the nabe from the heat and add the kamaboko and blanched spinach.