Mikkel Borg Bjergso, a 38-year-old former high-school science teacher who runs the Danish brewery Mikkeller, stuck his face into a bag of hops and inhaled deeply. It was a rainy February afternoon, and Mikkel, who makes some of the world’s most inventive beer, was visiting de Proef, a Belgian brewery in the town of Lochristi. The hops had been processed into unctuous pellets that resembled cat food, and they released a ripe botanical stink heavy on lemon grass and cannabis. “That’s nice,” Mikkel said, crumbling a few pellets between his fingers and nodding approvingly at the sticky green smear they deposited on his thumb. They were specimens of a strain called Polaris, developed by growers in Germany, which Mikkel had asked de Proef’s proprietor, Dirk Naudts, to purchase for use in a new Mikkeller beer. “They’re very fatty,” Naudts said.

Unlike most brewers, Mikkel doesn’t own a brewery. A typical Mikkeller beer originates in his brain as a far-fetched question: What quality of fattiness would a beer obtain if you sprinkled popcorn into the mash? What would happen if you dumped in a load of mouth-numbing Sichuan peppercorns during the brewing? How much fresh seaweed would lend a beer the right umami jolt? He then finds his answers by proxy, outsourcing the actual brewing to facilities, like de Proef, owned and operated by other people. Mikkel draws up detailed instructions for these fabricators to follow — specifying malt quantity to the milligram, mash schedule to the minute, bitterness to the I.B.U. — and the first time he tastes his own beer is usually when the brewer sends him a shipment and an invoice. “I don’t enjoy making beer,” he says. “I like making recipes and hanging out.”

This way of working is known as “phantom brewing” or “gypsy brewing,” and Mikkel is one of its best-known practitioners. His creations are adored not only on aficionado websites but also by chefs at Michelin-starred restaurants like Noma, in Copenhagen, and El Celler de Can Roca, in Girona, Spain, each of which enlisted him to design beers for their menus. As a phantom, Mikkel can source unwashed seaweed from the western fjords of Iceland, yuzu from Japan and avocado leaves from Mexico while leaving someone like Naudts to deal with the nitty-gritty of putting such ingredients into a beer someone might actually drink. And because he has so little overhead, Mikkel doesn’t have to worry about appealing to mass tastes. Which means more creative freedom. In any given year, a typical craft brewery produces maybe 20 different beers. Last year, Mikkeller made 124.

The number of phantom brewers is growing, and Mikkel, who got into the game in 2006, views this with a mixture of magnanimity and trendsetter’s pride. But he pays particularly close attention to one Brooklyn-based phantom brewery, because it is owned by his identical twin, Jeppe Jarnit-Bjergso. Jeppe started his brewery four years after Mikkeller began and, in an act of winking provocation, named the outfit Evil Twin. It is a smaller operation than Mikkeller, but similarly well regarded among connoisseurs. (Jeppe used to help Noma curate its beer selection.) The Bjergso brothers have opposite temperaments: Mikkel is reserved; Jeppe is an extrovert. And they are not on good terms, despite — or rather, because of — their shared infatuation with beer. They haven’t spoken to each other in more than a year.