I suffer terribly from what you might call a paralysis of wonder. When I become the custodian of something truly marvellous, notably beautiful, or a little bit rare, I worry so much about using it for a sufficiently special purpose that, more often than not, I fail ever to use it at all. My kitchen, in particular, is a graveyard of reverent neglect: a golden bottle of sunflower oil, pressed by monks in an ancient Georgian monastery, long past rancid; a little jar of barbecue sauce folded into my palms years ago by a grizzled pitmaster in Tennessee; a desiccated hunk of white truffle tucked in molding white rice; bags of international potato chips hanging on far beyond their sell-by dates.
Not long ago, a package arrived at my apartment, in Brooklyn, from a friend in the Bay Area, containing a new priceless gift: a dozen fresh yuzu fruits, plucked a day earlier from a tree in her mother’s yard. The moment I opened the box, two things happened simultaneously. One, my kitchen was suffused with the fruits’ intense, floral aroma. And, two, I vowed that I wouldn’t let these treasures go to waste.
“Treasure” is not much of an overstatement when it comes to yuzu. The knobbly-skinned Japanese fruits are among the most exquisite members of the citrus family: more floral than an orange and nearly as tart as a lime, with a scent that is dense and disarming, the Froot-Loops-y honey of a lemon blossom wrapped around an astringent armature of industrial floor cleaner (which is somehow exquisite), then magnified tenfold, then mailed to the moon. “The yuzu fragrance is entirely its own,” Shizuo Tsuji, a titan of Japanese gastronomy, wrote. It “resembles no citrus familiar to the West.”
The fruit is also a treasure in a more material sense. Yuzu trees dot California, an arboreal legacy of Japanese immigrants from the late nineteenth century, but their commercial growth there is limited, and the U.S.D.A. has a ban on the import of fresh yuzu from abroad—the fruit and the trees. So, for citrus aficionados living outside the farmers’-market radius of the California coast, processed, pre-prepared yuzu products are pretty much all we’ve had. In the rare instances when I’ve seen fresh yuzu for sale in the tri-state area, almost always at a Japanese specialty grocery, they’ve been staggeringly expensive, running fifteen to twenty dollars a pound. (In contrast, lemons are generally a dollar or two per pound.) I’m told that, among New York chefs, there is a thriving black market in fresh yuzu smuggled from Japan.
The fruit’s honeyed tartness is clear and lovely in all its packaged, processed forms—perfuming vinegars and hot sauces, infused into vodka and shoyu, tarting up yogurt and cheesecakes. If you were yuzu-obsessed, you could soften your lips with yuzu balm, garland your meals with yuzu salt, soothe your throat with yuzu tea, and dress your buttered toast with yuzu marmalade. But—as with all citrus—even the brightest processed-yuzu product is a tinny AM radio compared with the full, lush surround sound of the fresh fruit. A ripe yuzu is rough-skinned and yellow-orange, almost spherical, flattened slightly at the stem and the flower ends. Its skin is pitted and pockmarked, and often hangs loosely around its flesh. The fruit’s scant juice is puckeringly sour, but its rind is gently sweet, and rich in aromatic oils.
Yuzu is thought to have originated in China, but the fruit is most closely identified with Japan, where it is one of the nation’s essential aromas and flavors. It’s a key ingredient in ponzu sauce, the tangy blend of yuzu juice and soy sauce that often accompanies cold noodles or fried pork cutlets. It also lends zing to highballs, seasons potato chips, and is a favorite flavor for candy. On the winter solstice, bathtubs and onsen throughout Japan teem with whole yuzu, bobbling in the hot water to give bathers (including capybaras) a bracing soak.
My apartment’s bathtub is pitifully shallow, so a yuzu bath was out. The fruits have very little juice—they’re mostly pith and massive seeds—so squeezing out my entire stash, just for a couple of hasty at-home cocktails, seemed tactically misguided. I considered my bounty, wavering on the edge of catastrophic inaction, and arrived at a plan: the best part of a yuzu is what Tsuji described, in his book “Japanese Cooking: A Simple Art,” as its “marvelous aromatic rind,” so I decided to zest the fruits, using a fine-tooth grater to scrape off only the colorful and aromatic outer layer of the skin. I would use it to make yuzu kosho, a fiery-hot condiment of chiles, zest, and salt—it’s simple to make, keeps practically forever, and shows off all that’s wonderful about this exhilarating fruit.
As with many of the best condiments, yuzu kosho’s rich, complex flavor comes from a brief period of fermentation. The mixture is allowed to rest for a few days, giving the zingy freshness of the hot peppers time to relax into something deeper, as the floral notes of the citrus oils are drawn out by the salinity. The end result is a rough paste, glittering with salt and vividly green, suffused with the sharp, sour, sweet intoxication of yuzu. It’s intensely salty and blazingly hot; as such, it’s best portioned out in dots and dabs—a tiny pearl of yuzu kosho on top of a seared scallop or a meaty grilled mushroom, a tiny scoop blended into a vinaigrette or mashed into an avocado, or a pea-size dollop stirred, at the very last moment, into a bowl of ramen. If you don’t live in California—or you aren’t fortunate enough to have a friend who does, and is willing to send you yuzu care packages—you can buy yuzu kosho pre-made. (My favorite comes in a set of two jars, one made with green peppers and the other with red.) Or you can make it using another member of the citrus family: kosho of grapefruit (beautifully bitter), Meyer lemon (mellow and tart), tangerine (funky and sweet). Some people mix a slew of citrus zests together, in an attempt to replicate yuzu’s elusive, ineffable fragrance. I’ve tried, and it’s not quite right. Yuzu is yuzu; there’s nothing else quite like it.
A confession: I zested only three of my yuzus before a familiar doubt made my hand pause on the Microplane. Was this really the yuzu’s highest calling? Shouldn’t I save the rest of my bounty for some better purpose, yet unknown? My three-yuzu kosho came out to a tidy half cup, enough to punch up my meals for a month or two. The rest of my lumpen, pitted, squish-faced, beautiful fruits went into the crisper drawer—they’d last longer in there, which would buy me time to commit to using them. But fresh yuzu are so rare, so wonderful, so miraculous, that it took weeks to work up the courage. Don’t ask me what I saw when I finally opened the crisper drawer; I can’t bear to tell you.
Citrus kosho
Ingredients
20 grams citrus zest, from any whole, clean citrus fruits
80 grams stemmed and seeded fresh hot green chiles, like bird’s eye or jalapeño, finely chopped
10 grams sea salt or kosher salt
Directions
1. Combine the zest, chiles, and salt in the bowl of a small food processor and blend until a smooth, almost uniform texture forms. Alternatively, grind the mixture to a paste using a mortar and pestle or a suribachi.
2. Spoon the mixture into a glass jar and seal the lid. Let the kosho ferment in the refrigerator for five to ten days. Once it’s fermented, the kosho will keep in the refrigerator for up to six weeks.
