This sweet and flavorful sauce is commonly used for Unagi Don (Unadon/Unaju). It is super easy to make at home and it can be used for many purpose. I also used this sauce for Yaki Onigiri (Grilled Rice Ball).
- Combine mirin and sake in a small saucepan and bring it to a boil to evaporate alcohol.
- Add sugar and stir until sugar is completely dissolved. Then add soy sauce and bring it to a boil. Then reduce heat and continue cooking on simmer for 20 minutes. Turn off the heat to cool it down. You can store the sauce in the refrigerator.