True mirin, known as hon-mirin (本みりん), follows a similar brewing process to sake with one major difference: it is made using glutinous rice.
Mirin gives us a mild sweetness that balances the salty taste of the soy sauce. It also allows us to glaze sauces such as teriyaki and is an indispensable ingredient in slow-cooked dishes such as oyakodon.
Years ago, finding authentic hon-mirin was difficult, but it is gradually becoming more and more available in Europe. If you can’t find hon-mirin, the alternative is aji-mirin (みりん風調味料). Cheaper, aji-mirin is made from corn syrup, alcohol, rice and salt.
You can store mirin, tightly sealed, in a cool, dark place. If you get your hands on a bottle of hon-mirin, I recommend keeping it in the fridge to preserve its aroma.