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Chef Justin Cournoyer prepares a dish of radish and carrots with soil-infused butter at his restaurant Actinolite in Toronto.Kevin Van Paassen/The Globe and Mail

It's late June, and chef Justin Cournoyer is heading north of Toronto in his Subaru Forester to forage in the wilderness. He's on one of his biweekly pilgrimages to harvest wild bounty, such as chamomile, ginger, peas, woodruff or ground elder. These he will place into a cooler to take back to his small hyper-local Ossington Avenue restaurant, Actinolite. While he's out, he's also seeking an ingredient that the average forager might overlook: soil.

"You want soil that is near maples and pines," he says. "If it's too into the pines, it's too acidic."

He prefers not the silty topsoil that one could procure from a front lawn, but the stuff that is rife with pine needles, decaying organic matter and broken-down leaves. He wants the scents and sensations of an Ontario forest captured in a handful of dirt, and he wants to cook with that dirt.

"You smell it and you know it's good," he says. "It smells like camping."

Now most people are taught to keep their food and dirt separate, but earthiness is a highly desirable tasting note. It's perhaps inevitable that ambitious chefs like Cournoyer would attempt to distill the peaty, mossy, mineral flavours of the earth into an ingredient. Think of it as the ultimate expression of terroir.

When Cournoyer has the soil he needs, he takes it to his restaurant and boils it to 120 C in a pressure cooker to sanitize it. The soil particles are strained out, dried, placed into a sachet and sealed in a vacuum pack with butter. The pack is then cooked sous-vide for around four hours, until the butter is infused with earthy essence. Meanwhile, the soil's boiling liquid is reduced into a "tea," which is then whisked into the butter.

The final product looks like regular butter, but it's slightly musty, with traces of cocoa. It's evocative of the earth but not overpowering. Cournoyer uses it for the opening dish in his seven-course tasting menu. It's served without cutlery, forcing hands-on interaction. The radishes and carrots stand upright with foliage attached, as if they're growing out of the plate. The combination of soil-butter and root vegetables is rustic; the addition of wild grass (concocted into an oil and mixed with toasted breadcrumbs) adds a touch of grittiness. It's like taking a nosedive into a farmer's field. And yes, it actually tastes good.

Cooking with dirt is mostly a fringe practice in Canadian restaurants, but it might not be for long. Montreal's Toqué! chefs have steeped soil with water, sugar and glucose to make a woody caramel syrup, and they've also cooked eggs with a mixture of soil, dried branches and coriander to imitate the effect of a campfire. The idea can seem like a bizarre overreaching of extreme food culture.

As culinary trends go, it has been culminating (or would that be decomposing?) for years.

Revered French chef Michel Bras is often credited with being the first to translate the appearance of a leafy landscape into food with a dish called gargouillou, which he developed in the late 1970s. More recently, chefs such as Rene Redzepi (of Copenhagen's Noma) and Heston Blumenthal (of London's the Fat Duck) took that trompe l'oeil effect a step further by duplicating the appearance and texture of soil with breadcrumbs, olives, almonds and other ingredients. Mostly, the goal is to nudge dining guests into unfamiliar territory.

This concept of "edible soil" has spawned advocates across the globe, and it's now relatively common in restaurants with a modern or molecular bent. At Toronto's Marben, chef Rob Bragagnolo dots a tomato salad with clumps of "soil" created from dehydrated black olives and sourdough rye breadcrumbs. The texture is sandy, like you'd expect dirt to be, but the taste is savoury and salty. Similarly, Calgary's Market restaurant recreates soil with toasted hazelnuts, caramelized sugar and fresh thyme for its heirloom carrot salad.

"The point of this visual trickery is for a wow factor, so people will walk away with a memory," Bragagnolo says. "Sometimes you have to reach out to keep things interesting."

The idea of using actual soil in restaurants, though, is decidedly less common. Blumenthal traces the idea to Japanese chef Yoshihiro Narisawa, who is known for his soil soup featuring burdock, spring water and, of course, dirt.

"If soil is sourced and cooked properly, it can actually taste good," Narisawa said at a 2011 food symposium in Copenhagen. "Soil is so alive."

Historically, the practice of eating dirt is known as geophagy. And while there are claims that eating soil can provide nutrients such as iron or zinc, Dr. Keith Warriner, a professor of food safety at the University of Guelph, questions the trend.

"I've never heard of any nutritional benefits from eating soil," he says. He points out, too, that there is a risk of botulism or other bacterial contamination if proper sanitation measures are not taken. If soil is going to be eaten, he says, it should either be consumed in its raw state – so as not to activate harmful bacterial spores – or it should be heated to at least 120 C. Boiling is not enough to kill botulism, he says.

At Actinolite, Cournoyer credits one of his former sous chefs, Michael Lehmkuhl, for bringing the idea to the restaurant. Lehmkuhl had completed a three-month stagiaire at Noma, where he witnessed a pastry chef experiment with soil in ice cream. He was fascinated. "It was a new flavour," he says. "It was very familiar and yet very foreign."

Lehmkuhl wanted to introduce soil into his own cooking, and infusing butter seemed to be a clean, efficient way of doing so. After about two weeks of experimenting, he came up with the process.

Cournoyer, for his part, supports the idea of eating soil from a philosophical standpoint. It fits with his goal to evoke a connection to nature through cooking. But he also just likes the taste.

"If you have a carrot that came out of great soil, leave some of it on," he says.

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