Sienna Miller "smelt of fish for weeks" while preparing for 'Burnt'.
The 29-year-old actress trained with chef Marcus Wareing to learn the skills needed to play a chef de partie in the movie - in which she stars with Bradley Cooper - but it wasn't always pleasant.
She said: "I think I cooked 70 turbots in one day - my fingers smelt of fish for weeks.
"Marcus did shout at me during training. 'You can't hold your spoon like a f***ing shovel.' I was [his] favourite pupil."
The stunning star sported "a very sweaty face under a white chef's cap" in the film and found it a "relief" not to have to worry about her appearance.
She told Vogue magazine: "I think, at a certain point, you have to let go of any sense of vanity in films and start playing real character roles. It's a relief actually, for the focus not to be to look glamorous."
And director John Wells was very impressed with the actress' dedication to the role.
He said: "She always came to set prepared, ready to work, she trained very, very hard to simulate being a chef."
As well as her impressive work ethic, Sienna also makes filming fun for those around her.
Bradley said: "She comes ready to work but also ready to play and makes everyone around her feel at home."