Jennifer Schall describes best "If you’re not familiar with it, Italian buttercream is the smooth, light, and oh-so-buttery (but not quite as sweet) cousin of the powdered sugar version of buttercream that you are probably already familiar with. They’re in the same family (I believe the surname is “butter”), but they aren’t close cousins that grew up together. Nope, they’re like distant second cousins. I like to think of Italian buttercream as that sophisticated cousin who moved away to Europe to lead a far more glamourous life. You can judge for yourself, though."