How do you take your coffee? With a little egg, butter and cheese? In the Vietnamese capital, that’s how it’s served at the famous Giang Cafe.

On one of the endlessly busy streets in Hanoi’s Old Quarter, tourists and locals alike can be seen searching for the almost-hidden cafe down a narrow alley where the original cà phê trúng (egg coffee) can be found.

On the menu is an array of drinks but all anyone is ordering is this beverage, in hot or cold versions. The hot one, served with the cup sitting in a small dish of hot water to maintain its temperature, is almost too thick to drink, so I use a small spoon.

It doesn’t taste of egg – more like vanilla – and while I can taste the coffee at the bottom of the cup, the egg part is surprisingly light-tasting and not at all sickly, though certainly sweet. The cold option, laden with ice, is more of a dessert and tastes like coffee ice-cream.

At the counter, collecting payment, sits Nguyen Van Dao, whose father invented the drink in 1946 while working as a bartender at the city’s Sofitel Legend Metropole hotel. At the time, milk was scarce in Vietnam so whisked egg yolk was used as a replacement. Other Hanoi cafes have attempted to imitate the drink, but the packed venue offering the authentic version is still the most popular spot in town for an egg coffee fix.

Coffee powder, condensed milk, a little butter and cheese are also added to the mix, but Mr Nguyen won’t reveal all the details. “It’s a secret recipe,” he says with a grin over the sound of a blender furiously whirring away in the kitchen behind him.

• 39 Nguyen Huu Huan, cafegiang.vn

This story was published on The Guardian