Thank you for this! I want to make buttercream roses for cupcakes but am afraid the buttercream will melt. I'll try this :-)
If your recipe calls for all butter, use 1/2 (or slightly less than half) shortening. This will stabilize the buttercream and give it a higher melting point, but you'll still have the butter flavor. I live in SE Florida and am a prof baker; this works.