Mirin is a great liqueur that many Japanese people forgot how to enjoy.
If you ask your average Japanese friend if they ever had drunk mirin, they would look at you as if you went bonkers. They may even try to educate you, telling you that it is not for drinking but for cooking.
I remember in my teenage years, adults were talking about kitchen drinkers who drunk "even" mirin. Drinking mirin was seen as the final denigration.
And yet, mirin had a place akin to port wine during the Edo period. Its rich sweetness was much valued and mirin infused with herbs was ( and to a certain degree still is) an indispensable drink to mark New Year.
Much like you make sloe gin by infusing sloe in gin, mirin is made by infusing koji and glutinous rice(optional) into distilled alcohol, mostly shochu.
The recipe is something like below.
Koji: glutinous rice: distilled alcohol=1:1:4
Koji: distilled alcohol=1:2
The latter is supposed to be quicker to mature ( about 3 months?) but I think the former, which takes minimum of 6 months to mature, tends to have richer sweetness.
Of course, mirin's sweetness meant people used it in cooking, especially when sugar was hard to come by. But what damaged mirin as a drink is a combination of tax and advent of supermarket.
Japanese alcohol tax used to be very strict and, proper, drinkable mirin was not allowed on supermarket shelves for a long time. You needed to go to a proper wine shop for a bottle of mirin those days.
But, of course, there was a leeway. If you added 2% salt to mirin, making it too salty to drink but good enough for cooking, you could sell it in a supermarket. Also, it was much cheaper as it was technically not alcohol.
For many people, mirin is that salty sweet liquid, disgusting to drink, but good when you are stewing food, or making teriyaki sauce. I myself have never tasted proper matured mirin until well into my thirties, but when I finally did, it overwhelmed me by its complexity of flavor and taste.
I find it rather sad that once prized drink is so totally forgotten in its own birthplace.
Now, if you are wanting mirin just for cooking, you can pretty much substitute it by mixing rice wine and sugar. But properly matured drinkable mirin is a totally different story. That is something worth waiting for a year or two.
This year, I was surprised to find a bottle of mirin on a supermarket shelf in Britain. My memory was that mirin was one ingredient that was hard to get hold of in mainstream supermarkets.
I bought a bottle and only when I came back home, checked the label. Ingredients: Glucose syrup, water, rice, alcohol, corn syrup. Made in Japan.
Well, I don't blame the supermarket as it is what majority of my folks believe what mirin to be. But maybe it is worthwhile to start infusing some more now.