It’s the world’s best-selling spirit you’ve never heard of—and it’s growing while the rest of America quits drinking

Daniel Dae Kim, the actor, is walking Jimmy Fallon through the finer points of somaek, a popular Korean drink that mixes beer with the spirit soju. “Like a boilermaker,” Kim says on The Tonight Show, where he’s promoting his CNN series K-Everything. As with most drinking cultures around the world, there are rules. The youngest person should pour, though Kim, 58, takes up the job on Fallon’s behalf. He perches a pair of Korean flat metal chopsticks in parallel lines over a half-full beer glass...