For the first six years of his life, Audrey Hepburn’s youngest son didn’t realize his mom was a world-famous movie star.

“To me, my mother was Audrey Dotti,” says Luca Dotti, whose father was Hepburn’s second husband, Andrea Dotti. “I never realized she was Audrey Hepburn. I didn’t know she was a movie star. She always looked at my father like he was the center of attention.”

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Luca’s new book about his mom, Audrey at Home, features her favorite recipes, a collection of never-before-seen family photos, and a private side that few ever saw. Excerpted in this week’s issue of PEOPLE, it’s an intimate look at the Breakfast at Tiffany’s star, who preferred staying home to going out and simple plates of pasta to fancier foods.

“She was a simple country girl” says Dotti. “Her favorite dish was spaghetti with tomato sauce.”

As he writes in his book’s introduction, “Mum was adorable, of course, but I did not find her the least bit exciting.”

Dotti recalls how he was puzzled at 5 or 6 when journalists would ask him about “Audrey Hepburn.” “I’d say, ‘I don’t know who you are talking about. You must be mistaken. My mother is called Dotti,’ ” says Luca, a graphic artist and father of three who lives in Rome. “I didn’t know she was Audrey Hepburn until I was 6 or so.”

Luca – who has an older brother, Sean Ferrer (from Audrey’s first marriage to Mel Ferrer) – discovered her movies when they had a family movie night and his father screened Love in the Afternoon.

“Suddenly, there was my mother kissing Gary Cooper,” he recalls. “I remember perfectly because I was so embarrassed and I ran to my father and said, ‘Dad, this is serious. You should be upset. Mommy is kissing another man.’ So that explains how much I was aware that my mother could possibly be a movie star. I had no idea.”

Looking back, he says, his mother “wasn’t living her life as an icon. She didn’t live in a castle behind bars. She wasn’t driven in a limo. She was walking with her dog most of the time.”

“She stayed true to herself throughout her life,” says Luca, who’s donating a percentage of the book’s proceeds to the Audrey Heburn Children’s Fund. “It shows in how she lived her life and her choice of recipes. She never wanted to overdo. She wasn’t interested in making fancy, important dishes. She preferred dishes that were easy to make and healthy for her kids.”

“If you imagine my mother in fashion, she started with Givenchy and Valentino, but at that end of her life, she was happier in jeans and a T-shirt,” he notes. “It was the same in how she cooked at home. It was back to the basics. She didn’t have to impress anyone, really. It was what she loved and how she lived.”