Can my chocolate buttercream frosted cake sit covered on the counter overnight without the icing melting? I used cocoa instead of melted chocolate?
I frequently leave buttercream frosted cakes out over night and never had a problem. You dont want to expose it to high heat though. It should be ok at room temperature.
If it's a regular american buttercream with shortening or butter + powdered sugar, then yes, unless it is all butter and is particularly hot where you are. I'd be sure to keep it covered of course.