Hi Belinda! Cornstarch may help so long as it gets cooked long enough that it can thicken, so it would need to be boiled. It's used in German Buttercream. We don't have our own German Buttercream recipe though. This article found cream cheese frosting to do the best in the heat, which didn't require any cornstarch. If you haven't read through the article we'd recommend doing so. 

• Reply