Lightly smoky and full of umami, Mentsuyu is a Japanese soup base used either hot or cold in a multitude of noodle dishes. You can easily make it at home with sake, mirin, soy sauce, and katsuobushi (dried bonito flakes). This Mentsuyu is concentrated.
In a saucepan, add the sake, mirin, and soy sauce.
Add kombu and katsuobushi.
Slowly bring it to a boil over medium-low heat.
Then, reduce the heat to low and simmer for 5 minutes. Then turn off the heat and let it cool.
Pass the mixture through a fine-mesh sieve (reserve the kombu and katsuobushi for another use—see below).
To Use the Mentsuyu
This Mentsuyu is concentrated. In general, the mentsuyu-to-water ratio should be 1:2 for a dipping sauce for Zaru Soba/Udon, and 1:4 for Udon/Soba Noodle Soup. Please adjust the taste of your dipping sauce or soup broth by adding more mentsuyu or water.
You can store the Mentsuyu in a mason jar in the refrigerator for up to a month.
What to do with the spent katsuobushi and kombu?
Use the spent katsuobushi and kombu to make Homemade Furikake Rice Seasoning. You can also save the drained katsuobushi and kombu in the freezer until you're ready to make the furikake.