American Repertory Theater Artistic Director Diane Paulus has a knack for developing works that make it to Broadway. Finding Neverland, Pippin and The Gershwins’ Porgy and Bess all premiered in Cambridge before heading to Manhattan.

Paulus’ track record could bode well for the future of her new musical adaptation of the indie film Waitress. It’s currently in previews at the ART, where the creative team spoke about its evolution and why adapting the film for the stage has been a bittersweet journey.

Director Diane Paulus didn’t see the film “Waitress” when it first came out in 2007, but a few years ago, legendary Broadway producers Fran and Barry Weissler told Paulus they thought it could make a great play.

“Full confession, the DVD sat on my desk for about a year before I found the time to watch it,” Paulus recalled during the final phase of the rehearsal period, “and as soon as I did I knew this show had the heartbeat of a musical.”

For Paulus, Waitress has all the right ingredients. Take Jenna, the main character. She waits tables at a diner, is stuck in a stifling, abusive marriage and yearns for a better life. Then she learns she’s pregnant. Paulus finds the fictional Jenna’s situation riveting – and very real.

“This is the story of a waitress struggling with these issues and yet when I saw the film I thought of all kinds of people I know – girlfriends of mine – who have also struggled with the kinds of issues that this character struggles with.”

In the movie Jenna pours her churning emotions into creatively named pies she bakes each day for the diner. They’re a form of therapy – and escape – from her controlling husband, Earl. Actress Keri Russell plays Jenna in the film and tells her friends at the diner about her latest crusty concoction: “I Don’t Want Earl’s Baby Pie.”

Her friend jokes, “I don’t think we can put that on the menu board.”

Theater director Diane Paulus calls the film version of Waitress dark, but quirky and funny, and she says Jenna’s character is complicated and vulnerable.

“For me that translated into, you know, ‘who the heck can write this score?” she remembered.

Paulus found her composer/lyricist outside the musical theater world in Grammy-nominated singer, songwriter Sara Bareilles. She topped the Billboard charts with hits such as, “Love Song.”

At their first meeting, Paulus asked Bareilles to watch Waitress, hoping the musician would connect with its main character Jenna – and offered up some advice.

“Don’t worry about, ‘how should this be adapted? What is the outline for the musical?’ Just go with your heart, your inspiration, see where it takes you,” Paulus told her.

“The door felt like it opened,” Bareilles said looking back. “I felt like I really began a relationship with this character.”

During the interview with 90.9 wbur, standing at an upright piano in a rehearsal room at the ART, Bareilles sang the first song she wrote after watching the movie. It’s called, “She Used to Be Mine.”

Some of the lyrics go, “It’s not simple to say, most days, I don’t recognise me, these shoes and this apron, that place and its patrons, have taken more than I gave them …”

Now the song “She Used to Be Mine” is the centerpiece in the ART’s new musical.

Another critical ingredient in this stage adaptation of the movie is actress Jessie Mueller who plays Jenna, the waitress. She won a Tony Award for her role as Carol King in the Broadway musical, “Beautiful.”

Speaking about her current role in Waitress, Mueller mused, “Poor Jenna Hunterson never had therapy, if she had it would be a very different play.”

Instead Jenna’s therapy are pies. So many pies. In the film her visually playful, revealing pie-making moments are captured through monologue, dialogue and intimate camera work. Actress Jessie Mueller elaborated.

“You get a beautiful close up on Keri Russell’s eyes, and you know what’s going on in her head – well you can’t do that on stage, but you can have the character sing their inner thoughts. The music is where you get to hear the inner-workings of all these characters.”

The Waitress screen-to-stage recipe has been tweaked over the past two years or so, and the plot line was restructured. Jessie Nelson joined the team to write the play’s dialogue, or “the book,” as it’s known in the business.

“If you’re too loyal to the movie, it won’t become a musical, so it’s this delicate dance of both honouring the spirit but allowing it to really live and breathe in another medium.”

Writer Nelson and the rest of the team were also sensitive about honoring the spirit of the movie’s creator Adrienne Shelly. In 2006 Shelly – who wrote, directed and had a role in Waitress – was murdered soon after finishing her film. Nelson told me she never had the chance to meet her, but she knows Shelly’s work and her family well, and Shelly’s screenplay is always on her mind.

“When I was writing I really carefully went through it and tried to bring her voice into it whenever I could,” Nelson said, “as if she was another collaborator in the room.”

Producer Michael Roiff of Night and Day Pictures was close friends with Adrienne Shelly and retained stage rights for their film after selling it to Fox Pictures at the Sundance Film Festival in 2006. He’s been part of the Waitress musical adaptation team, too.

“In a lot of ways that’s been my role in the development, is (I’m) the guy who says, ‘well, this wasn’t really what our intention was.’”

When asked about the emotional challenges of re-working Shelley’s screenplay he said, “The hardest thing on this journey for me has been knowing that’s she’s not sitting there next to me. And there’s a bittersweet quality to all of this. But I just hope she somehow knows and is happy about all of it.”

Roiff likes to think Shelley would be pleased with how her movie is being re-imagined as a musical for the stage. Waitress the musical takes on real-life issues such as true friendship and love, domestic abuse and the joys and fears that come with the prospect of motherhood, while being entertaining at the same time. Plus, it’s packed full of Jenna’s beautiful pies.