According to legend, egg coffee was invented in 1946 by the proprietor of Giang Cafe. At the time, milk was very expensive and scarce, so Mr. Giang developed a recipe using egg yolk instead. Nowadays, you can find egg coffee in many cafes in Hanoi, but no so much in the rest of Vietnam. There have been many alterations to Giang's recipe. Probably most often, cà phê trung is made by heavily beating egg yolk, sugar, and condensed milk then pouring it on an approximately equal amount of Vietnamese coffee. You may also come across menus calling it ca phe trung nong (hot egg coffee) or ca phe trung sau (egg coffee with milk), or you may find variations like ca phe trung da (iced egg coffee). When your coffee is served, give it a good stir before you drink it. It's very sweet -- something to slowly sip and savour in a beautiful atmosphere.