It tastes sugary, but it's a vegetable. It resembles a sweet potato, but is related to Jerusalem artichokes and sunflowers. It hails from the Andes, but was little-known outside South America until it gained popularity in Japan.
Yacon is a tuber that resembles a jicama cross-bred with a water chestnut and it has started to appear in diverse dishes at Sydney restaurants and cafes.
Rhys Hart, of Jack of Harts & Jude at Engadine, serves a salad of peeled yacon ribbons with fresh guava, walnuts, goat's cheese and prosciutto. ''My customers love it,'' he says, comparing the taste to fresh sugar cane.
At Marrickville's Cornersmith cafe, Alex Elliott-Howery has experimented with pickling yacon, making yacon syrup and serving it thinly shaved in a salad with radish, poached pear and pomegranate.
''It keeps its crunch, which is what we like about it,'' she says.
This season is only the second yacon harvest for NSW growers such as Field to Feast in Campbelltown and Going Organic in Towrang, near Goulburn, and the first time local produce has been sold commercially. It's still only grown in small amounts.
The chef at Restaurant Atelier in Glebe, Darren Templeman, first spotted yacon on Field to Feast's order sheet late last year. ''I was like, what is this? Then I thought: OK, I'll just give it a go,'' he says.
Researching online, he saw he could reduce yacon juice into a heavy syrup, which he first used in desserts. Now he creates a dark yacon caramel with butter and white-wine vinegar that goes into a savoury eschalot tatin. ''It lets the eschalot shine instead of being overpowered by a conventional sugar caramel,'' Templeman says.
He also makes a sous vide confit of yacon, which he uses in a sweet and sour salad with turnip and baby radishes, and has created a dish of cocoa-roasted venison loin with yacon, carrot puree and warrigal greens.
''Yacon is very versatile,'' Templeman says. ''It's amazing how it's not been utilised more by chefs.''
For Jessica Aissou of Going Organic, yacon was a surprise crop - it grew from an unidentified rhizome she received from a supplier. Research and tastings convinced her of its potential, and her entire second harvest was snapped up this year by the chef and owner of Wafu in Surry Hills, Yukako Ichikawa.
Though Ichikawa intends to close the restaurant, she will stay open during August and serve her dish of yacon slices with sesame seeds and a white miso, brown-rice vinegar and agave syrup dressing.
The root was introduced to Japan in the 1980s; the country now grows one of the largest crops outside South America. A mistake many people make when cooking with yacon for the first time is treating it like a potato, Ichikawa says. It is more similar in taste and texture to a nashi pear. Rather than boiling, mashing or roasting it, in Japan the root is fried in tempura batter or used in stir-fries. Ichikawa also brews the leaves into a medicinal tea.
Yacon has a reputation as a health food. In Japan, it is used to treat hypoglycaemia - it contains a low-GI form of fructose that doesn't get absorbed by the body, so it doesn't cause sugar-level spikes. Yacon syrup is used as an alternative natural sweetener for diabetics, as well as being a honey substitute for vegans.
Catherine Fiefia at Field to Feast says she and her husband, Hapi, began growing yacon ''on a whim'' two years ago, starting with six plantings.
They now grow a much bigger crop and sell it to organic restaurants and health-food stores, as well as to customers at markets around Sydney, including The Sydney Morning Herald Growers' Market. For those unsure of how to approach yacon, Fiefa offers advice on its many facets, including the foliage. ''Apparently, you can use the leaves in cooking, like a banana leaf,'' she says.
The Sydney Morning Herald Growers' Market, Pyrmont Bay Park, Pyrmont (opposite The Star) is on Saturday, 7-11am.
For Cornersmith's radish, pear and yacon salad recipe, see cuisine.com.au.