Portman makes directorial debut in Venice

"We have so much time off between films as actors that you tend to get restless and you want a creative outlet, and there is not always acting work that fulfils that need," she said.

"I have been working now in films for 16 years...it was exciting to know what a director goes through and also to create something completely on your own.

"When you are an actor of course you are creating something but you are serving someone else's vision and ultimately it's someone else's creation. To have authorship is ... and feels like a more adult job," she added.

Getting Bacall on board was like fulfilling her "wildest dream", Portman said.

"It's so exciting to see someone with that much experience and that much wisdom on screen. It's rare."

Portman, who shot to fame as a teenager befriending a professional killer in Luc Besson's 1990s hit "Leon", has featured as Padme in the second Star Wars trilogy and won an Oscar nomination for best supporting actress in "Closer".