Heat a pot of water and bring it to a boil. Cook the soba noodles until al dente, about 5 minutes. Drain the noodles and set them aside in a bowl.
In the meantime, heat 1 1/2 cups of water in a pot and bring it to a boil. Add the Mizkan (Bonito Flavored) Soup Base, Sriracha, Naruto, mini bok choy, and mushrooms. Boil for about 1 minute.
Turn off the heat and pour the soup over the soba noodles. Top with sliced hard-boiled eggs and serve immediately. Add more Sriracha for extra heat, if desired.
Notes
Mizkan (Bonito Flavored) Soup Base is a magical condiment that you can use to make a variety of authentic Japanese dishes: cold soba dipping sauce, the broth for noodles such as udon and soba.