Behind Willi Lehner’s house in Blue Mounds, Wisconsin, under a hillock of craggy earth supported by a wall of stone slabs, is a bunker that’s supposed to withstand tornadoes, hurricanes, and earthquakes. The manufacturer of the kit it was made from, Formworks, even claims that one of the same design survived a simulated nuclear blast. But Lehner , a 52-year-old cheese maker, isn’t preparing for the apocalypse—he’s just trying to protect his wheels of bandaged cheddar, farmstead Käse, Havarti, and Gouda.

“The rind of a cheese doesn’t like humidity that goes all over the place,” says Lehner. “That’s where the biggest effect is—on the surface of the cheese. If you get irregular, wacky swings in humidity you get splits and cracks in your rind, and when that happens you get mold growing into your cheese.”

Not that he’s trying to discourage mold. Inside the cave, resting on cedar shelves, 11- and 38-pound wheels of English-style cheddar wrapped tightly in muslin are covered with splotchy, gray microbial colonies that after months of aging help the cheddar develop the exquisite caramelly flavors that can send chills jolting down the back of your legs.

“The mold that grows off the surface of these cheeses gives off real small microscopic rootlets called mycelium that actually grow into the cheese and give off enzymes that the mold can feed off of,” Lehner says. “And those enzymes leave flavor behind. Vacuum-packed cheddar is never ever going to attain that kind of flavor.”

That flavor won Lehner and his Bleu Mont Dairy a blue ribbon at the American Cheese Society Conference in 2006. He had inoculated the winning cheese with mold spores scraped from classic English cheddars, but it also benefited from the ambient Wisconsin microflora. Microorganisms that act on some of his other cheeses come from the soil on his property, which sits at the edge of the rough Driftless region of southwestern Wisconsin, an area that escaped the glacial scraping of the last Ice Age. Lehner got the idea to harvest microorganisms from local dirt after a tour of farmstead cheese makers in the UK, but his appreciation of the influence of terroir on cheese developed in his youth, during a summer spent herding cows and making cheese in the Swiss Alps.

Lehner’s father, Billi, was born in the Swiss canton of Lucerne, where he went through a three-year apprenticeship making Emmenthaler before emigrating with his wife, Mary, in 1952. They drifted around a bit, farming and logging, before he learned about Wisconsin’s Little Switzerland, in the region around New Glarus. He figured if he could make a go of cheese making anywhere, that would be the place, and found work at a cheese factory in nearby Mount Horeb, which he managed for 21 years. Now home of the Grumpy Troll brewpub, that plant is where he introduced Willi and his five siblings to the trade. At first Willi’s jobs were cleaning up and building boxes, but in his teens he got involved in making, waxing, and packing cheese.

In 1975, when he was 19, Lehner took off for his ancestral homeland. For years he traveled around Europe, India, Nepal, China, and Tibet, but he kept his base in Switzerland. One summer he and his brother Peter found work escorting cattle high into Alpine pastures. They’d milk the cows every morning and churn butter and craft traditional mountain cheese: “We made it in a copper kettle over a wood fire, just like it was done 200 years ago,” he says. He compares the result to Gruyere or Italian Piave and says this is where he grasped the value of using milk from animals that grazed in pastures. “Up on the alp the cows ate grasses and plants and flowers that didn’t grow down in the valley. And the color of the butter we produced up there was just so intense—because of the carotene—and the flavor that was imparted to the butter ... that made a huge impression on me.”

After ten years abroad Lehner returned to the States and began working in the cheese plant his father had bought in 1979—Valley View Cheese, in South Wayne, Wisconsin, now owned and operated by Lehner’s brother Hans. After a few years he resumed butter making. “I started experimenting with various cultures and adding them to cream to sour it before I churned it into butter,” he says. “I was making small batches of butter and packing by hand.” No one else in the area was producing cultured European-style butter at the time, and when Lehner started offering his wares at Madison’s Dane County Farmers’ Market, the butter was a hit. Every three weeks Lehner would buy four ten-gallon cans of cream from a cheese factory and haul it out to nearby Ridgeway, where his friends Anne Topham and Judy Borree of Fantome Farm make goat cheese. “It was a lot of work to produce 180 pounds of butter,” Lehner says, and over time he began to burn out. Five years into it, in 1991, his churn broke and he quit on the spot. Within a few months he was approached by the founders of the young Organic Valley dairy cooperative and asked to develop their butter program. Today the cultured butter made from his recipe is sold across the country.

In the meantime Lehner was experimenting with cheeses based on his father’s recipes from the old country. He developed relationships with factories around the state and, taking advantage of the different equipment available at various facilities, was able to produce several varieties. He aged them, wrapped in vacuum-sealed plastic, in a walk-in cooler in the basement of his solar-powered house, where he lives with his partner, Quitas McKnight, and their kids, Chen and Inea.

Ever since, Lehner, who says he’s “always experimenting,” has taken a series of steps back from the process of modern industrial cheese production, moving toward a traditional approach closer to the one his father grew up with. First he started making cheese with organic milk, then with raw organic milk. In 2003 he procured a license to operate a small temperature-controlled curing room off the straw-bale greenhouse next to his house. This let him age his cheeses without using plastic, which prevents shrinkage but also shuts out the thousands of varieties of microbes that can contribute to the development of an extraordinary cheese. During this phase of experimentation with surface curing he also made his first bandaged cheddar, wrapped in cloth and painted with lard to prevent it from cracking as it ages.

He ordered some bandaged cheddars from the Ann Arbor gourmet emporium Zingerman’s, including the English cheese that sets the standard for the variety—Montgomery’s cheddar, made from milk produced on a 500-year-old family farm. He collected mold scrapings from each, mixed them with water in a blender, spritzed the liquid on the wheels, and let them age. In 2005 he received a state grant to visit 16 farmstead cheese makers in England, Ireland, and Scotland. While on tour Lehner and McKnight spent time with giants of the English cheese world, including the cheese makers at Montgomery’s. But it was in Ireland—on a visit to Giana Ferguson of Gubbeen Farmhouse, which specializes in washed-rind cheeses—that Lehner began to think about using Wisconsin mold. “She was really passionate about encouraging the microflora in your region,” he says. “She drove the point home: don’t kill something off unless you know what it is, because most microbes are pretty harmless.”

A few weeks after their return Lehner was digging around in the garden. “I picked up a handful of soil and I smelled it and thought to myself, ‘This is where our microbes are,'” he says. “And so I went out in the woods and looked for a place where there wasn’t any deer poop and scraped away the leaves and took off the top inch of soil.” He brought it back to the house, shook it up in a jar with some water, and let it sit overnight. After straining the solution and letting the remaining particles settle, he spritzed it over four small Havarti-style wheels. He kept them in his basement, away from the others. Every day, he says, “I’d go down there and wet them down, and then within a week’s time I had peachy beautiful growth starting on the cheese. It had this really wonderful mushroomy earthy smell to it.” After a month Lehner and McKnight tasted it, and “it was magnificent,” he says. After another month they sent it off to a lab to have it tested for harmful organisms and, given the all-clear, began selling Driftless Select Earth Schmier at the farmers’ market.

“It’s in the line of Limburger, but Limburger is real potent and kind of in one dimension, whereas my Earth Schmier cheese—because I usually make it out of raw milk—it’s got a lot of complexity to it,” he says. Last summer Lehner sent it off to the ACS competition in Portland, where it tied for third place amid competition from renowned cheese makers such as Cowgirl Creamery, based in northern California, and Michigan-based Leelanau Cheese Company, whose aged raclette won best in show.

Since then, Lehner’s made eight batches of the soft Earth Schmier, which have all sold out in a few weeks. (He started his ninth just last week.) It’s the one cheese people inevitably mention when they write or talk about him. In March the New York Times took note of it in a roundup of Dairy State cheese makers, calling Lehner “the off-the-grid rock star of the Wisconsin artisanal cheese movement” and quoting him as saying “If I make it, they will buy it.”

Lehner, who still sells only at the Dane County market, says he didn’t intend this to sound boastful. But it bears out even with what he considers his less successful experiments, such as a batch of cheddar that smelled like “barf” and reminded him and McKnight of a hard Italian cheese, a style neither particularly cares for. Rather than toss out all 2,500 pounds of it, they branded it “Italian cheddar” and made sure marketgoers who showed interest tried a sample before buying it. Most turned it down, but occasionally someone loved it, and after about two years it sold out. “I think last year was the first time in about five years we haven’t had someone at least once during the market season come and ask if we have any more Italian cheddar,” says McKnight.

A few weeks ago Lehner brought out the first bandaged cheddars cured in the cheese cave. In a few more weeks he’ll introduce his first raw-milk bandaged cheddar, made from organic milk purchased from his friend Mike Gingrich of Upland Cheese Company. The vaulted cave is 1,600 square feet and can hold up to 30,000 pounds of cheese. Lehner has sunk about $130,000 into the structure since he began building it in May 2006, but he expects to break even in 15 years based on his energy savings alone. The cheese cave maintains a temperature between 51 and 59 degrees Fahrenheit year-round without artificial heating or cooling, and the minimal amount of power he needs—for lights, a fan, and a small dehumidifier—comes from his solar panels and wind tower.

Inside it’s musty and smells of mushrooms and the whiff of ammonia given off when proteins in the cheeses break down (usually a sign of overripening). Currently there are about 7,000 pounds of cheddar, Gouda, farmstead Käse, and a raw-milk Gruyere-style variety called Lil’ Will’s Big Cheese that Lehner inoculates with the same solution he uses for the Earth Schmier. He plans to enter four or five varieties in this year’s ACS competition, to be held in Chicago in July. Meanwhile he’s slowly ramping up production, but he doesn’t want to make so much cheese that he has to hire full-time employees. As a result his distribution is still limited—the only place Bleu Mont cheese is currently available here is at Bin 36, which offers the bandaged cheddar. (Eno, in the Hotel InterContinental, has featured Lil’ Will’s Big Cheese in the past.)

In a second room two enormous wheels of Emmenthaler that Lehner’s curing for a friend are slowly growing a downy white fuzz. He says this brine- and whey-washed Swiss is not unlike the sort his father produced during his apprenticeship, but he knows of only one other maker of it here. “I’m trying to encourage microflora here, not discourage it,” he says. “The molds have been around longer than we have.”

For more on food and drink, see our blog The Food Chain.