Sam Adams Utopias, a new "extreme beer," doesn't taste anything like the Bud you drank last night. It's not carbonated, it's 25 percent alcohol, it's served at room temperature, and a 25-ounce bottle will cost you a whopping $100.

Daniel Bradford describes the beverage in elegant language: "Silky, rich, creamy, with slight caramel notes. . . . It has much in common with a very balanced single-malt whisky." If properly cellared, it should age very well, adds Mr. Bradford, an aficionado of the libation.

Bottles of this stuff sell at auction on eBay for $150 to $300. But this isn't Scotch — it's "extreme beer," a growing phenomenon at the far edges of America's 25-year-old craft-brewing movement.

Koch recently spent a beautiful day ensconced in his brewery's lab and surrounded by small glasses filled with beer samples. He was oblivious to the nice weather outside because he and two of his brewmasters were testing this year's entries for the Great American Beer Festival. The three tasted "Triple Bock," a yet-to-be-marketed sherry-like barley beer that is aged in an oak cask. Koch and his brewers like the way the new beer is developing. "It's a taste that nobody has ever put into a beer," he boasts.

It's what Koch calls an "extreme" beer and what Boston Beer specializes in—a premium, niche product that appeals to select drinkers, not the masses.