An unusual source of caffeine is whipping up buzz across social media.  The drink known as egg coffee, which originates from Vietnam , is made by blending egg yolks with sugar and condensed milk. When the mixture is poured on top of strong Vietnamese coffee, the result is a sweet, fluffy drink that tastes like a dessert — with many social media users comparing it to marshmallow. In Vietnamese, the drink is called cà phê trứng, which translates to “egg coffee.” It’s believed to have originated