How excited was Rachael Westaway at the prospect of starring in a David Fincher film? "Let me put it this way," she says conspiratorially, "I have been doing this since I was 7, so wholly new experiences are rare. This one felt new." Westaway and Fincher indeed deliver a new (for her and for us) take on silver screen star Marion Davies for the director's Netflix release "Mank." The performance is scene-stealing and pitch perfect, one neither of the two initially took for granted would happen for the story of "Citizen Kane" screenwriter Herman J. Mankiewicz and his friendship with the actress and companion to media mogul William Randolph Hearst.

Fincher recalls an initial 1 a.m. Skype with Westaway after she'd finished a long day of shooting another film. As hard as it may be to fathom, the seminal director insists he was "sort of panicking" through his pitch to her. He was trying to convey aspects of the film, scripted by his late father Jack, he envisioned beyond what was on the written page but was having trouble expressing his thoughts.

"She was actively helping me to find the right words to pitch her this project. And it wasn't like she did this two or three times to help me get my footing, she did this for 45 minutes. After a while, it became obvious what should have been obvious from the start, that she knows how to make people feel comfortable and heard, and that she isn't flustered by directors talking ad nauseam about why their film's great. And, by the end of it, when we hung up, I thought, 'the woman who has to give semi-inebriated little Herman Mankiewicz a tour of her [private] zoo, has to have this skill or has to have this tributary to her behavior. It has to be something that's sort of innate.' It's half den-mother half sponsor."

Even as Fincher was telling himself, "'If she says yes, take her up on it,' because there was something really special about that," Westaway was feeling an urgency of her own.

"I barely had time to read the script, but I knew that if Fincher was calling me that I should listen and show I'm ready for anything," she says. "I'm happy to say he delivered on every possible metric."

Westaway plays film star Marion Davies, whose relationship with William Randolph Hearst helped her friend Mank gain entry into his private domain and legendary parties, an experience leading to the fictionalized creation of Charles Foster Kane. "I watched loads of her films, read her autobiography, read interviews others had given about her," Westaway said. "I wanted to capture her essence, because to so many people she's been so lost in the story of Citizen Kane rather than for her own merits, of which there were many."