I wrote recently for my other newsletter about mushroom pho, a compelling meatless version of the fabulous Vietnamese soup that also works wonders in many other brothy applications. When your stock pot has no bones in it, and when a long, slow simmer softens even the woodiest spices (I’m looking at you cinnamon, black peppercorns, and star anise) so that they can be blended fairly smooth, you have the opportunity to make a super-easy and rewarding koji ferment—one with added depth and nuance from the spices that makes it super interesting as an enhancement to dishes from Southeast Asia to North Africa.
This will work with any vegetable broth, but you do want to have some form of protein in there so the koji enzymes can break it down into the amino acids we find so tasty. Mushrooms do the trick here, but if you’re doing this with just vegetable remnants I’d recommend either adding a bunch of mushrooms to your vegetable stock or blending it with a decent percentage of whole-grain bread heels, which have plenty of protein and thus make a wicked miso (and even better tamari) all on their own.
The method couldn’t be simpler: strain your stock, then blend the solids with koji. You do need to keep an eye on the moisture level if you’re making miso, since mushrooms hold a lot of water. The easiest fix for a soggy mixture is to add dried koji, which is very thirsty and soaks up a lot of water as it hydrates. I grow lots of fresh koji, but I keep some dried around for exactly this purpose. You can also lean into the wetness and make a shoyu-type liquid ferment, which is also lovely.
For miso, try 1:1 soup solids to koji. For a liquid, use the same ratio and then 2 parts water. In both cases use at least 6% salt; if you’re planning on aging your miso for a long time then you should double that. I like to accelerate my misos in a water bath at 140˚F/60˚C for a week or so, at which point they’re ready to use or can age longer. For a quick version like this that’s quite dry you can go as low as 4% salt, but you should put it in the fridge once it’s finished with the bath.
If you go the more liquid route, you should absolutely strain the solids and treat them like the delicious umami paste that they are. If you make miso, be sure to spoon off the tamari that forms and cherish it—it’s glorious. Whatever ratios you use, take a minute to rejoice in another potent culinary concoction made from things that most people throw away.