My standard buttercream is a boiled sugar buttercream. Karo, sugar, and butter. Basically you make a meringue and you add softened butter. It works fantastic, makes the lightest buttercream, stable even in the hottest and most humid of midwest days.
But, I have no idea why it works or how it works. When I add the butter it causes the whole mixture to break, then as I add more butter it pulls back together and becomes this great melt in your mouth stuff. But why? Is it emulsification? Homogenization? What causes it to happen?