In her Los Angeles studio, Julie Simon is turning a miniature carousel on top of a cake she's making for a 1-year-old's birthday. The mechanical carousel is painted with roses and fluffy clouds. Pink-and-blue saddled horses with gilded manes and tails glide up and down on poles. "Everything you see except for these poles — those are metal — everything is sugar," Simon says.

When it is finished, the cake will be decorated with butterflies, flowers, 24-karat gold dust and a framed portrait of the birthday girl and her mother. Simon says she can’t reveal the name of her client, the mother, who is a reality TV star. (She signed an nondisclosure agreement.) But Simon, who looks younger than her 49 years, isn’t really in this business so she can name-drop. “I live in this world of imagination,” she says, “creating really cool things and making sugar look like different things and making people happy.”

Simon’s cakes are without exception ornate, lavish and almost entirely edible. When you enter a room, they demand to be looked at like the monumental sugar sculptures that graced banquet tables in 18th-century France. She says artist Marc Chagall is her biggest inspiration. “He creates these things that feel like you’re in a magical world, and that’s what I want to create.”

Simon has always had a sweet tooth and began baking when she was a girl. She worked her way through “Mastering the Art of French Cooking,” making Julia Child’s chocolate mousse and pear custard tarts, then studied Wilton decorating tips and books by Colette Peters. When she was 28, Simon made her first ambitious cake: a Sylvia Weinstock recipe with sugar blossoms, honeybees and butterflies. Peters and Weinstock are both established cake artists based in New York. “The aesthetics of food, even when I was young, came into play because I wanted things to look so beautiful, like putting Pirouette cookies around a cake,” Simon says. “I got so into those little choux pastry swans.”

She also pays close attention to how food tastes. On one visit to her studio, I sampled her chocolate truffle torte with chocolate ganache. The interior layers were frosted with praline buttercream. Each bite was rich and velvety, and very satisfying for a chocolate lover like me.

In September, Simon partnered with fellow Yale University alumna Gillian Wynn to open Julie Simon Cakes. They don’t have a storefront and instead work with event planners and take word-of-mouth orders, which they fill at Simon’s home studio in central Los Angeles.

Each cake is unique. Simon doesn’t have a staff and says the larger ones require at least 100 hours of her time and cost the customer roughly $10,000. Smaller cakes start at $2,500. “I’ve never bought an expensive cake in my life,” says Simon. “I just make stuff.”

Simon grew up in a musical family on Manhattan’s Upper West Side. She’s the niece of singer Carly Simon and the daughter of composer Lucy Simon. Simon has sung with her mom and aunt at the Apollo Theater in Harlem. In her 20s, she was a singer-songwriter who also played guitar. “I always thought I would be a singer, and that was my dream,” Simon says. “I was going to be a rock star.”

But she lost a recording deal with Epic in 1999 and decided to take a job in HBO’s digital division. She went on to work for Time Warner, Lifetime and Fox. Ultimately, she did not find the media business fulfilling. “My priorities really shifted, and I thought, ‘Why am I doing something that I don’t feel really passionate about?’ ” Simon says.

Since she started making cakes for a living, the orders have been pouring in. Simon made a showy silver-and-gold cake for art dealer Jeffrey Deitch for a party honoring artist Ai Weiwei. The cake was inspired by a 17th-century Dutch still-life painting and featured a gravity-defying arrangement including irises, lemons and arching stalks of wheat.

Writer and director Lady Kinvara Balfour hired Simon to make a baby-shower cake. Simon decorated it with 10 kinds of lace, blackberries that look like they were just plucked from the vine and birds sitting beside their tiny nest. All of it was sugar. To form her roses, pine cones, thistles, lilies of the valley, tulips and kumquats accurately, Simon studies plants at the Huntington Botanical Gardens in San Marino, Calif., and at the Conservatory Garden in New York’s Central Park. Her blossoms might be ripped or browning. There might be holes in leaves where an insect has taken a bite. That’s because she likes to portray the life cycle of a flower, from bud to decay.

“She’s like a jeweler, how she works,” says Deborah Jaffe, a friend who photographs Simon’s desserts. “She goes into a realm where she’s so hyper-focused and it’s so exquisite.”

Bronson van Wyck, an event planner in New York who has worked with Beyoncé, Alicia Keys and the past three presidents, is also a fan. She got his attention with her Gustav Klimt cake, in which Simon re-created the artist’s “Portrait of Adele Bloch-Bauer I.” “There’s something that’s so lyrical and beautiful about creating something that is the absolute perfected expression of someone’s vision,” says van Wyck. “And it’s ephemeral, and it’s only going to be shared with the people you love.”

Back in the studio, Simon prepares a few final flourishes for the 1-year-old’s birthday cake. Once it is finished, she will deliver it personally, a service she provides for every customer. She has flown cakes on private jets and commercial planes from the Silicon Valley to New York.

Simon begins making sugar blossoms. First, she uses a motorized pasta roller to roll out blush-colored gum paste. Next, she cuts the dough into teardrops and carefully stretches each one into a translucent, paper-thin petal. To add texture, she presses veins into each petal with a food-grade silicone mold. Her tools include wooden skewers and knitting needles, and it takes an hour and a half to make a single rose.

“I’m in the most creative time of my life,” she says, preparing to start on the butterflies. “It’s been amazing. I feel like someone’s going to pinch me and I’m going to wake up.”

Abbie Fentress Swanson is a reporter and radio producer in Los Angeles.