Picture a cake. It’s frosted or iced, isn’t it? Often, that’s the best part. And more often than not when we’re thinking about frosted cakes — the ones coated in a thick and creamy outside layer — we’re imagining a particular style of frosting that’s often flying around the Great British Bake Off tent: buttercream.

Invented in the 1950s, there are six styles of buttercream that bakers know and love, or if you’re a contestant on GBBO, perhaps fear: American,