“Creaming” butter and sugar is an essential first step in ... it’s important to remember that overly soft butter will also not cream properly. Butter that is too soft will begin to melt ...

The one problem with this is that you can combine sugar and melted butter but you can't actually cream them ... You can see this in the mixture, as properly creamed butter and sugar will be ...

Cream the butter and sugar, as above, also adding the cocoa powder. Allow the melted chocolate to cool for 10 minutes before adding to the whipped butter and sugar. Beat until well combined.