Buzz
Yuzu koshō is like a burst of sunshine on your taste buds. This fermented paste, made with yuzu, chilies, and salt, delivers rich umami with a bright citrus twist. A while back, some friends and I discovered it in a soy dipping sauce during dinner in New York. None of us had tasted anything quite like it before. Later, as we dug into broiled fish, we realized it was the same incredible flavor we had encountered earlier. The waiter grinned and said, “That’s the koshō,” as if he had explained it many times before. And so, my obsession began.
You can easily purchase yuzu koshō, but I prefer to ferment ingredients myself. This curiosity led me to dive deeper into understanding koshō. Fresh yuzu is not only expensive but also rare in the United States. However, if you imagine a hybrid of lemon, lime, and orange, that's essentially what yuzu is. There’s a resilient yuzu variety specifically cultivated for the U.S., and I’ve already ordered one. Hopefully, this will make it more accessible in the future.
In the meantime, we’ll have to get creative by applying the koshō-making technique to other fruits and vegetables.
Citrus Koshō
Whenever there’s citrus in my house, I make sure to zest it and add it to my koshō. You could start by purchasing a variety of citrus, or take a cue from me and head to a location where citrus thrives. I spent a couple of days in Arizona this winter, juicing citrus with friends, like a madman, zesting every single grapefruit, orange, or lemon that crossed my path. All that zest eventually turned into a vibrant koshō stored in a half-gallon jar, now the obsession of everyone who visits. You can easily create your own version at any scale you wish.
Ingredients:
Grated citrus zest (Feel free to use any citrus you like, but a blend of different types gives the best outcome, in my experience.)
15% non-iodized salt, measured by weight
Hot peppers, adjusted to your heat preference
Collect all the zest you can find and weigh it. Perform the calculation to figure out 15% of the citrus weight, then add that amount of salt into your food processor. Blend the two together in short bursts for about eight seconds. Transfer to a bowl and set it aside.
Next, add in the peppers, but only as many as you’d like. For a fiery koshō, I suggest using jalapeños or Thai chilis, but keep in mind that a little goes a long way. Personally, since I prefer only a mild kick in my paste, I use 5% of the total paste weight, including the salt. I slice the pepper in half, remove the seeds, and toss it into the food processor to pulse again, just enough to incorporate the pepper. Add the peppers slowly, one at a time. They will mellow as they ferment, but only a bit. If you want, you can skip the peppers entirely and just use citrus, but I wouldn’t want you to ruin your batch by over-spicing it.
Take the mixture and transfer it into a jar with an airlock. Use a spatula to pack it tightly, making sure there are no air pockets. Give the jar a few taps on the table to help settle it. Clean the rim, then seal it with your airlock. If you don't have an airlock, simply open the lid every few days to let the carbon dioxide escape.
Over the coming months, your koshō will transform into a rich, citrusy umami delight. There are endless ways to use it – right now, my favorite method is mixing a teaspoon of it with olive oil, rubbing it over a whole cauliflower head, and broiling it. It's also great added to soy sauce, and many restaurants use it as a substitute for Maldon salt they might otherwise sprinkle on dishes. You can stir it into your fried rice or ramen, rub it on steak before grilling, and the uses are truly limitless. Once you try it, you’ll be hooked and will find yourself using it regularly.
Gather your koshō-making tools:
A popular citrus zester for effortless zesting: Deiss PRO Lemon Zester
A large jar for fermentation: Ball 32-Ounce Mason Jars (pack of 2)
An airlock to keep the jar sealed: Ball Fermentation Lids and Springs
Garlic scape koshō
I was already sold on koshō when one of my fermentation mentors, Jori Jayne Emde, shared a post about a green garlic koshō. I make mine with scapes. I know people rave about scapes, but in practice, they can be challenging to work with because of their strong flavor and tough texture. As a gardener, I always end up with an abundance of scapes each year, and I'm never sure what to do with them. They also flood farmers markets.
Her recipe was incredibly simple: Weigh your scapes, add 20% of their weight in salt, blitz them together, pack them in a jar, and let them mellow with an airlock. After about six months, the koshō became my absolute favorite kitchen staple.
I use it in salad dressings and as a seasoning for meat, especially on whole chickens before roasting. It’s also a fantastic addition to cassoulet beans, and adding just a touch to a coddled egg is pure bliss.
Koshō, aside from being irresistibly delicious, is an excellent way to reduce food waste. You’re taking ingredients you might not normally use (like scapes, zest, etc.) and turning them into something extraordinary. Even if all you ever do is add it to soy sauce, making koshō is still well worth the effort.
