A few months after essayist and screenwriter Nora Ephron died of leukemia in 2012, her son, New York Times writer Jacob Bernstein, was doing a profile on documentary filmmaker Lisa Immordino Vreeland. She’d recently finished the film “Diana Vreeland: The Eye Has to Travel,” about the well-known fashion editor. When he asked her what her next project was, she said she was considering doing a film on the art collector Peggy Guggenheim, but mentioned there was one other project she might “put in front of that.”

“What’s that?,” Bernstein remembered asking her. “And she said ‘Nora Ephron.’

“And I said, ‘Well, I think there might be someone in front of you.’ “

At last night’s New York premiere at the Museum of Modern Art of Bernstein’s film “Everything Is Copy — Nora Ephron: Scripted & Unscripted,” the writer-turned-filmmaker told Variety that he knew he had to get to work immediately before someone else told his mother’s story, as he’d heard about several documentary filmmakers who were interested in tackling the subject, including Susan Lacy of PBS’ “American Masters.”

He said he didn’t think merely writing about her would be enough (“I didn’t think that I was going to do a better book about my mother than she wrote herself”) and though his background is in print, he said “that doing a documentary was remarkably similar to the pieces we do at the New York Times.

“We did this oral history on Donna Summer after she died, just sort of talking to people in that era about where their lives had been and where her life had been, and then I did a piece about a therapist who committed suicide and just reconstructed the last days of his life,” he said. “And I knew that we would try to reconstruct her death, that that would be a piece of this. I think that documentary films are a good bridge between narrative films and what we do as journalists.”

“Everything Is Copy” covers Ephron’s entire life, from growing up with two screenwriter parents in California to becoming a celebrated Esquire columnist in New York to her troubled marriage to famed journalist Carl Bernstein to becoming a Hollywood screenwriter and director. Along the way, we see Ephron use every piece of her life as fodder for her writing — the life philosophy her mother gave her that gives the film its title.

The film weaves together dramatic readings of her essays along with interviews with her sisters, close friends and the actors and directors she worked with, with Meg Ryan recalling Ephron’s quick, often cutting wit and director Rob Reiner recounting the origin of the famous faked orgasm scene from “When Harry Met Sally.” But the most prominent voice is Ephron’s own. “I somehow stumbled on to the fact that she had read her essays for the books on tape,” Bernstein said, “and it began to occur to me that you could somehow have her narrate her documentary that way.”

The most difficult interview to get for the film was the subject closest to him, as Jacob said it took him two years to convince his father to participate in the documentary. As covered in the film, Ephron ended their marriage when she discovered Carl had been unfaithful, and turned the fallout into the book “Heartburn,” which she later adapted for filmmaker Mike Nichols; suffice to say, he didn’t come off looking great in either. “I think it took a lot of psychological pressure and the realization that I might not come over for Thanksgiving,” Jacob said, to get his father to change his mind.

“My father is in a very happy marriage at this point; I don’t think he was thinking when my mother died that ‘now we get to go through this again.’ I think he had totally reasonable concerns about what this might end up being in this current era of fame,” Jacob said. “You think to yourself: There were all sorts of things it could have been and ways it could have wound up, where it just ends up being misguided and exhibitionist. And I think he was concerned about that, and understandably so.”

Beaming with pride at the premiere, Carl admitted his son “had to kick me pretty hard in the ass” to get him to participate, but eventually he came around and allowed himself to be interviewed in the film, in which he talks honestly about falling in love with Ephron and praises her quick with and honest assessments about love and heartbreak. “Before I finally said, ‘Okay, I’ll do it,’ we had had many, many talks about the film, about Nora, about the marriage, about me.”

In order to agree to participate, Carl said he needed a few guarantees from his son. “One, that it was his film. That he had the final cut, and that it was his vision, that he was doing the work,” Carl said, adding that he finally relented because “he’s my son, and I should do this. It was important to him, it was important to the project, so I said ‘ok, So here I am.'”

“Everything Is Copy” will premiere on HBO on March 21.