Cult Melbourne croissanterie Lune attracted long lines and waits of up to three hours when it opened its first Sydney pop-up store at the Queen Victoria Building on Friday morning.

Hundreds of people queued to try the decadent $15.50 Belgian truffle croissant, a World Chocolate Day collaboration between Lune and Australian chocolatier Koko Black.

The first person in the line, Saki Akinakao, arrived at the pop-up store at 5am, when temperatures were as low as 9 degrees.

“I tried Lune croissants in Melbourne and they were so good, I had to have one again,” Akinakao says. To celebrate her arrival, she was presented with a free extra croissant by Lune founder and pastry chef Kate Reid.

The one-off creation, available at select Koko Black stores and the pop-up store on George Street until July 9, took about five months to develop and was inspired by Koko Black’s smooth, creamy Belgian truffles.

The twice-baked croissant is filled with Koko Black cocoa frangipane and 70 per cent Guanaja fondant, and topped with mascarpone chantilly cream, tempered chocolate shards, salted cookie crumb and Belgian truffles.

“It’s so crazy delicious,” Reid tells Good Food.

After trying a croissant, it became clear why so many people were willing to wait for hours.

“I assumed it would be too rich when I first saw it, because of all the cream on top, but the cream magically balances out the richness of the chocolate to create this perfect little package.”

After trying a croissant, it became clear why so many people were willing to wait for hours. The pastry was buttery and flaky, the filling rich and sweet without becoming overwhelming. It was the type of croissant you don’t want to share.

There will be 800 croissants available across the four Sydney stores each day of the pop up, with sales limited to one croissant per person.

For many Sydneysiders, such as home baker Stephanie Davies, the pop up was their first opportunity to taste a Lune croissant, dubbed the “world’s best” by The New York Times.

“Lune croissants are the gold standard,” Davies says, adding that she was prepared to stay in line “for as long as it takes”.

“I’ve been waiting for the Lune store to open in Sydney for over a year.”

The opening of Lune’s first Sydney store on Oxford Street in Darlinghurst has been delayed to early next year. Last week, it was announced Lune was already planning its second Sydney store, set to open on Castlereagh Street in Martin Place.

“We could not be more excited for the Sydney stores to open, it’s been the longest time coming,” says Reid.

“This time next year, there will be two Lune stores in Sydney.”