"He should not exist," Pasek says. "It's difficult to say if he's a better singer or actor. Our score is more pop than Broadway music, and the way he completely owns that style is so impressive."

The production ends its Arena Stage run today, but is poised to reappear at New York's Second Stage Theatre next spring.

"I'm 18 for the next two years, if anyone asks," says Platt, who turns 22 next month.

Platt's career is certainly coming of age. Movie audiences know him as the upbeat misfit Benji in the two movies, easygoing comedies about college a cappella singing groups. He's now on screen as a gay bartender who adores Meryl Streep's character in .

"To have something on film where I'm looking at Meryl Streep and she's looking at me and we're talking to each other," Platt says, "that's all you can ask for."

Not that Platt is only now getting a brush with the big time. He's a Hollywood kid whose dad, Marc Platt, was once president of production at Universal Pictures; the senior Platt's producing credits include the movie and the musical .

Platt followed his three older siblings in a musical theatre programme, where he fell in love with and . By the age of nine, Platt was appearing in annual musical concerts at the Hollywood Bowl. By 11, Platt was starring in an eight-month tour of the musical , the acclaimed musical by Tony Kushner and Jeanine Tesori about a Jewish boy and his family's African-American housekeeper in 1963 Louisiana.

"I'd really only ever really been around white Jewish people my whole childhood," Platt says with a laugh. "So to be around those amazing black singers was really inspiring."

His parents were careful not to shove him into showbiz and they offered ice cream as bribes for young Ben to go to soccer practice. He was a good student at the private Harvard-Westlake School in Los Angeles, but he chose Columbia University so he would have access to the New York stages.

Just before the autumn term in 2011, though, Platt landed his first movie role - Benji in - so he deferred his Columbia enrolment for a year. When he started school a year later, another big gig came - the role of Elder Cunningham in the Chicago production of - so he left school after only two months.

He starred in for 10 months, then returned to New York for a year-long gig in the same part on Broadway.

This year has been almost entirely dedicated to , except for the big Ang Lee movie he shot in Atlanta, , based on the Ben Fountain novel.

"It was definitely a choice," he says. "I think if I had been interested in films, my dad would have been equally supportive. I certainly grew up going to sets and seeing him work, and I knew a certain amount about the film industry. I just never was quite in love with that process."

The part has always been Platt's. Pasek and Paul loved him several years ago when he auditioned for their musical . He was too young for that show, but the songwriters flagged him for this.

"The director and I talked about always making sure that the audience knows what Evan's intentions are and what's going on in his mind," Platt says. "If you feel like you don't understand him, that's when you start to not be on his side. That's the thing that's so beautiful about this writing: You feel like you really know this kid. And there's nothing quite like a musical to feel like you understand somebody inside and out."