Founders Kentucky Breakfast Stout’s run as one of the craft world’s most prized bottles is impressive for its staying power. Born in 2003, the early days of bourbon-barrel-aged beer, the first batch of KBS filled two Jack Daniel’s whiskey barrels — which are neither bourbon or from Kentucky — with the coffee-infused Breakfast Stout. After the first tasting, Founders was hooked on the experiment. Soon, the recipe was tweaked to what we enjoy today: barrels from all the big Bourbon county producers and an amplified Breakfast Stout recipe that takes the beer above 11 percent alcohol.

Like most strong stouts, KBS takes roughly a year from brew day to bottle and spends most of its time aging in oak. But Founders has one big advantage that likely sets KBS apart: gypsum mines. Running under Grand Rapids and now converted to storage space, Founders rents air-conditioned caves to store 9,000 barrels — also containing Backwoods Bastard and a handful of experiments — that would never fit in the brewery. Yes, it’s odd for barrels of one of the world’s great beers to sit around the corner from pallets of butter sticks and stacks of all-but-forgotten legal documents, but the dark, constant-temperature rooms (about 40 degrees) create consistent aging conditions. Most brewers follow the model of the Kentucky bourbon rackhouses that warm and cool with the wild swings of summer and winter weather. This method, whether intentional or for lack of refrigerated space, produced undoubtedly phenomenal beers. But it’s not how KBS is made, and just maybe, it’s the difference.