Stevenson crafted his pralines - chocolate shells with soft centers - by lacing the chocolate with exotic fruit flavors. He won a Renault Kangoo award with "Belgian Chocolate Master" written on the side and was featured on Belgian television.
But he soon heard that a lot of chocolatiers thought his victory had been beginner's luck. And there was another problem.
"Firstly, I'm not a chocolatier," said Stevenson, a tall skinny red-head, with a self-effacing smile, before adding: "I'm also Australian."
He set out to prove his doubters wrong.
An Aussie representing Belgium in chocolate was an assault to Belgian national pride, which is based largely on prowess in making chocolate, brewing beer and delivering fattening foods such as fries and waffles.
The Belgian love of chocolate goes back to the 19th century, when they shipped cocoa from Congo, their new African colony. Brussels cemented its position as world chocolate capital in 1912, when Jean Neuhaus created the first praline there.
Stevenson, 36, came from a different world: Brisbane, on Australia's east coast, and the math's faculty of a university, where he studied in the hope of becoming an actuary, a specialized statistician who figures out insurance premiums.
But a part-time job in a patisserie proved more fun than all the numbers, and he ended up working on pastry full time. After two years he decided to leave the country.
"It's not fantastic in Australia," he says. "I understood that if I wanted to improve, I had to come to Europe."
His aim was always chocolate competitions, but he figured pastry studies were the best route, as patisserie lends chefs a diverse range of skills.
He enrolled in a school in Munich run by celebrated patissier Robert Oppeneder. The master spotted Stevenson's talent and made him his assistant.
After working in London at the luxury Lanesborough Hotel, he headed to Brussels to make a name for himself in competitive chocolate. He married, and his father-in-law put him in charge of pastry at Le Saint Aulaye, his cake and bread shop.
Stevenson's day job lasted from 4 a.m. until 2 p.m. Then he stayed in the kitchen to train at chocolate.
He made cakes for four hours, and then practiced sculpture, creating flowers and bamboo reeds made of chocolate. Then he would hone his praline technique for several more hours, blowing through 30 kg of chocolate a week.
Sugar-free Red Bull kept him going till around midnight, when he'd crash and sleep till 3:30 a.m. Then it was time to get up for work.
"I did it just for the chocolate competitions in Belgium," Stevenson said. "You have to do your job. And after your job, you have to practice."
Chocolate has such a strong taste that it drowns out many other flavors, such as strawberry or pineapple, he says. So instead, he chooses acidic ingredients to mix in.
The praline that helped him win his first Belgian Chocolate Masters in 2008 was laced with lemon thyme and passion fruit.
His praline victory in the 2009 World Chocolate Masters came after he added in kalamansi, a strong, sour citrus fruit native to the Philippines, and tonka bean, a wrinkly, black bean used as a vanilla substitute.
"If you can imagine you're a judge, you're going to eat a lot of chocolates," he says. "You have to give them one that tastes fresh to get a high score."
Stevenson credits math's studies with developing his analytical mind, which helps him to solve structural problems and understand the chemical structure of his creations.
"If I have to make a swan out of chocolate," he says, "I break that problem down into small pieces, and attack each piece, like you would with a math problem."
After making the world's best praline, Stevenson tried his hand at his own line of commercial pralines. But he found it too hard, as he didn't have all the necessary equipment and machines, and is staying at Le Saint Aulaye for now.
Meanwhile, the Brussels chocolate community has become more international, and continued competition success has helped him gain acceptance.
He's also training young chocolate and pastry chefs.
"Now I'm a mentor," he said.
