Step 1

Set a small sauce pot over medium heat. Measure and pour in the Mirin, soy sauce, and sugar. Stir to combine. Allow the mixture to come to a boil. Then reduce the heat to medium-low and simmer for 15 to 20 minutes, stirring occasionally.

Step 2

The eel sauce is done when it has reduced by about half, and is thick enough to set up a little bit on a sushi roll. Remember, it will continue to thicken as it cools so remove it from the heat when it's just a bit runnier than desired.

Step 3

Cool completely, then move the eel sauce to an airtight container and store it in the refrigerator for up to a month.