Vietnam’s most extravagant cup of joe, cà phê trứng (“egg coffee”), has a less glamorous backstory than its lavish appearance suggests. Born out of necessity and quick thinking, this clever hack was invented to cope with wartime dairy shortages.

In Hanoi, coffee drinkers rely on a steady stream of condensed milk to balance out the strong Robusta brew served in most coffee shops. In fact, simply ordering a cà phê sữa (“milk coffee”) is interpreted as hot Robusta coffee with sticky-sweet condensed milk. What happens when the milk runs out? The remaining breakfast staples—eggs and coffee—are called upon for greatness.

First created in Hanoi in 1946, egg coffee is the brainchild of Nguyen Van Giang. In response to the pressures of a milk shortage caused by the French War (also known as the First Indochina War), Giang whisked in egg as a much-needed substitute while bartending at the Sofitel Legend Metropole Hotel. Giang’s signature drink became such a hit that he opened Café Giang in the wake of its success, where his son still serves the legendary egg coffee.

Egg coffee is, of course, more than just an egg cracked into your morning brew. Modern Vietnamese egg coffee is as much a dessert as it is a drink. The recipe now features heavy Robusta topped with a combination of hot, whisked egg, sugar, and creamy ingredients ranging from condensed milk to cheese and butter. Actually drinking the beverage is such a decadent experience that it hardly alludes to its wartime origins. The viscous, sugary concoction might be likened to liquid tiramisu, or a coffee-flavored Cadbury Crème Egg.