Eating the Kiso Valley #1: Kiso’s Finest Miso

Welcome to ‘Eating the Kiso Valley’ – a new series of articles covering the culinary side of life in the Kiso valley. In today’s post, we’ll be taking a look at some of the best miso money can buy, and trying our hand at making some shio koji.

(Content Warning: expect photos of extremely cool and incredibly gross mould within)

Early in 2020, just a few months after moving to Nagiso, my wife and I drove to the nearby ‘Big Town’ Kiso-machi (population: 11,000) to see the sights. There, walking along the Kiso river on a chilly autumn day, we spotted a small miso shop, and eagerly decided to have a look inside.

This already marked something of a personal growth for us, since in the past, as true skittish millennials, we had often struggled to summon the courage to go inside old, dimly-lit Japanese shops or restaurants like this.

If you’ve ever spent time in Japan you’ll know the ones I mean – barely translucent windows; a hand-written sign outside arcanely hinting at their exact line of business; one single dim lamp barely visible, giving you the vague but extremely strong premonition that an old man is having a nap somewhere deep within, and that being so foolish as to actually enter this place of business during business hours would invite a great and terrible fury.

My wife is Japanese, and even she doesn’t like going into places like this. But since moving to the countryside we’ve outgrown this weakness, and have bravely entered more menacing old shops than you could shake a stick at (partly because a good 80% of all shops here are menacing old shops). So into the miso shop – Koike & Co. in English, or 小池糀店 in Japanese – we went.

The best miso in the world, hands down. I’m so earnestly in love with it I can’t even bring myself to put a joke in this caption.

And bloody lucky thing we did, too, because that day we stumbled upon the best miso we’d ever tasted. And what’s more – a miso that completely changed the way I cook. Because while Koike & Co. sells some lines of regular (albeit extremely delicious) miso, they also sell a line of miso that’s very special indeed. Because it tastes almost exactly like cheese.

That’s not due to some chemical concoction designed to ape the taste of cheese, or because someone’s been artlessly mixing cheese directly into the miso. Instead, it’s all thanks to some very specific strains of mould that the nice man explained to me but I didn’t really understand.

As someone who basically only eats vegan nowadays, it was honestly a dream come true. And whereas before I rarely used miso outside of a few basic Japanese dishes, now I use this miso in all kinds of things. I’ve even developed a vegan cheesy stew using this miso and some nutritional yeast that I’m honestly very proud of.

So, ever since our first visit, we’ve been going back and buying this miracle miso almost every time we’re in town. Fast forward to last week, when we found ourselves back in Kiso-machi showing a city-slicker friend of ours around, and decided to drop in to buy some more miso. This time, though, we were in for a a new surprise entirely:

It lives.

The nice man was back. He remembered me as the nice foreigner who can speak Japanese, and I quote: ‘well’. And this time he was eager to show us a little bit more of their unique miso-making process.

And trust me, this is really unique: a friend of ours makes their own miso every year (which we’re planning to do as well once we move (that move scheduled for some time in the year 2038)), and it looks nothing like these cheesy fungus pillars. It’s usually just a big pot with some mush in it that changes colour and gets sort of lethargic after a few months. Koike & Co.’s miso-making method is really, really something to behold.


In part due to the mould, over time the miso grows a kind of crust, like a block of cheese or a delicious scab. That crust then turns thick and hard, and sprouts a kind of grey mycelia carpet of hair. Really gnarly stuff.

According to the nice man, you can’t make this kind of miso in modern buildings, as they’re too well-ventilated. You need (and I’m getting PTSD flashbacks of rainy season just talking about this) the kind of stultifying, lace-your-lungs-with-mould humidity that only a proper, traditional Japanese house can give you

Anyway, obviously seeing how the sausage is made didn’t turn us off the stuff. If you think that’s weird, then, well, okay. I don’t really have an argument against that. It’s just really good miso, you know? And it’s not like you eat the hairy scab. Just fly to Japan and come try this miso, then you’ll understand what I mean.

Just looking at it gets your appetite going.

With our pack of miso in my arms like a newborn child, I spotted something else they were also selling: rice koji.

If you don’t know (and as far as I’m aware, it’s not suddenly become massively popular in the west) rice koji is just cooked rice that’s been innoculated with a specific strain of fungus (Aspergillus oryzae according to google). This fungus ferments the rice, turning it into sugars and other delicious science stuff.

Rice koji (you can also make koji with barley, soy beans, etc.) can be used to make a bunch of Japanese food products (including miso itself, but also soy sauce, sake, and so on).

This is rice koji. It looks a lot like rice krispies. Do not confuse the two.

We decided to buy some rice koji in order to try our hand at making two Japanese condiments: shio koji (or koji salt) and soy sauce koji. The first can be used in place of regular salt for all kinds of things (like marinating food, making pickles, or even salting meat, if you’re into that kind of thing), and the second can be used in place of soy sauce for (again) all kinds of things (like adding it into ramen, or sauces, dressings, etc.).

Making them is extremely easy: for shio koji you just mix the rice koji with water and a whole load of salt. With soy sauce koji it’s just rice koji and soy sauce. Then you leave them for about 5 to 7 days, stirring them once per day. And there you have it: delicious, umami-packed condiments.

I’ll let you know how they are at some point (I know full well I’ll probably forget).

Measuring the ingredients. Pro cooking tip from personal experience: do not put in double the amount of salt listed in the recipe. That is too much salt.

If you don’t use miso (and I know most people in the west tend not to), I’d definitely recommend you give it a try. You probably won’t find cheesy miso like this one, but even regular miso (white, red, or awase) is a great ingredient to get to know. One that unlocks a whole host of delicious Japanese meals.

And if you can get your hands on some shio koji (I’ve seen some American cooking shows use it, so you can definitely buy it somewhere) I’d also recommend giving that a try too.

Finally, if you ever find yourself in Kiso-machi for any reason, check out Koike & Co. They’ve recently done a bit of renovation (as you can see in the picture at the top of this post), and now boast a fancy new sign and 100% guaranteed non-menacing internal lighting.

Really, the huge number of great ingredients like miso and koji and soy sauce etc. etc. makes me kind of baffled that vegetarian and vegan food isn’t more of a thing in Japan. There’s a long Buddhist tradition of vegan food of course, but it’s more a historical note for most people, and while I’ve been to a good few places that make great vegan food in Japan, it’s really not caught on at all like it has in countries like the UK and the US.

But there’s so many amazing ingredients just packed with rich, meaty flavour that I use all the time in my vegan cooking. Shiitake mushrooms, kombu kelp. Soy sauce. Miso. And now koji.

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