Iron Man star Jon Favreau has revealed his culinary skills were below par before he started filming Chef.

The 47-year-old, who wrote, directed and stars in the indie comedy, trained with chef Roy Choi and attended cooking school to prepare for his role as chef Carl Casper.

“I was a good bachelor cook when I was younger,” he said at the film’s British premiere at the Backyard Market in London’s Brick Lane.

“My Italian grandma made sure I knew how to cook enough items so I wouldn’t always have to buy food from a restaurant. But beyond that, I didn’t have a lot of skill.

“For this project, chef Roy Choi oversaw my training and the menu so I first went to culinary school, then I started working in a kitchen in Roy’s restaurant and worked my way to be a line cook.”

His Marvel co-star Mark Ruffalo and TV chef Andy Bates braved the rain to support Favreau at the event, which featured street food by London outfit Kerb.

The father-of-three claims he is now taking on Seth Rogen with meat cook-offs.

“Seth Rogen likes to tweet pictures of his home-made projects. They look pretty good,” he said.

“I’ve been trying to work on briskets of my own so I’ve swapped recipes and (we can) see how we stand up to one another.”

Favreau said he had made the most of his new-found skills and techniques.

“I like pasta, steak and cooking the foods that are in the movie. I learnt those things so that I knew what I was doing and now I like to do them in my life.”

The New York-born film-maker said his movie, which stars Sofia Vergara, Dustin Hoffman and his previous Iron Man co-stars Robert Downey Jr and Scarlett Johansson, is a love letter to the culinary world.

“If you love food … and chef culture, this movie tries to get those details right,” he said.

“And it also serves as a wonderful backdrop to a story about following your dreams and a father and son bonding on a road trip.”