When you make chocolate buttercream, you'll usually have two options for the buttercream: cocoa or melted chocolate. For my favourite, most intense chocolate buttercream icing recipe, I use both!
Put the butter in a large mixing bowl and beat with an electric whisk until really pale and aerated.
Sift in the icing sugar and cocoa powder, then add 1 tbsp of hot water and 1 tbsp vanilla.
Mix on a low speed with your electric whisk until everything is combined. You can then turn your beaters up to full speed and beat until light and smooth. It will take at least 4-5 minutes.
Add the cooled melted dark chocolate. It's important that it's well cooled or it will melt the frosting. Whisk until well combined and smooth.
Transfer your buttercream into the piping bag fitted with a star nozzle and twist.
You'll have enough to pipe the frosting on top of the 12 cupcakes in very generous rising swirls, or enough for 24 cupcakes with more modest frosting.
Video
Notes
Bonus cake decorating tips!
You can frost a perfect rose on top of a cake. Just start from the middle and ice outwards, keeping it as flat as possible.
To stop sugar paste from sticking to your work surface, dust with cornflour, not icing sugar. Icing sugar leaves unsightly white streaks and dries the sugar paste out, causing cracks, whereas cornflour dissolves invisibly back into the icing.
Water with a tiny bit of icing sugar in it makes perfectly good glue. This might be the last time you pay for a bottle of sugarcraft glue!
A bit of screwed up foil can make the centre of a sugar paste flower look far more realistic. Once you’ve cut out your little flower and put a little ball of contrasting icing in the centre, just squish some screwed up foil against the middle a few times and you’ll get a lovely, dimpled effect.
Use salted butter in butter icing, rather than unsalted, because it tastes better and lasts longer. I try to keep our salt intake low, but slightly salted butter brings out the sweetness in buttercream.