Now, many of you might be trying to recall seeing it on the menu and some of you might be trying to kickstart the taste memory.
And among you, there must be those who might be wondering 'what is so unique about it?'
Well, it is a coffee, but "not just coffee", as journalist Harriet Marsden likes to put it.
In her article, which has appeared on The Independent website, she mentions how this unique hot drink, which has come from Australia or may be New Zealand (actually it's a bone of contention), is becoming popular among coffee-drinkers in the United Kingdom.
"It epitomises the Third Wave or artisan coffee scene, now accounting for often more than 10 per cent of coffee beverages ordered in quality UK coffee shops," Jeffrey Young, founder of The London Coffee Festival, tells The Independent.
So, what is it?
Double shot of espresso blended with steaming and slightly frothed organic milk, according to the McDonald's UK website.
And in Marsden's words, it is "Richer and stronger than a latte, creamier than a cappuccino, smaller than an Americano, with a drier foam or "microfoam"".
Further, this foamy drink should be served in a cup no larger than 5 or 6oz, according to Ian Boughton, editor of trade magazine Boughton's Coffee House.
Now, what is so unique about it?
Its uniqueness lies in the way it is crafted (made).
First, only the whole milk should be used and the milk-heating technique has to be perfect. It should be heated to about 65 degrees.
According to Lavazza's head of training Dave Cutler, the milk "needs to be very well stretched and well spun to make sure it has plenty of tight bubbles - a micro foam - which makes it very, very creamy."
"Whole milk is steamed and folded through the coffee, creating a velvety texture before the drink is presented, usually with latte art on the surface," Cutler adds.
It is the uniqueness and the craftiness, with which it is made, the flat white is slowly gaining popularity among the public.
"Since its arrival into the UK, the popularity of this now king-of-coffees has skyrocketed. This can be put down to the fact that the public's interest in coffee in general has seen unprecedented growth," says, Andrew Knight, founder of independent coffee roaster Andronicas.
"People now understand the difference between a really great coffee and a substandard one."
And going by its popularity among the experts, there, very well, a time may come that it may challenge the "global ubiquity of the cappuccino and the American consumerist latte". (ANI)