Allow to cool until lukewarm. Add the butter and beat with an electric whisk for 5 minutes. Beat in the icing sugar and then the buttermilk. Place in a piping bag and pipe onto cake.
Was it a gorgeous layered cake with rich chocolate frosting? We doubt it ... Add cocoa mixture in 2 batches, alternating with the buttermilk. Divide batter evenly between pans.
Dollop the frosting onto the cooled cake ... layer on malty maple syrup, splash in tangy buttermilk, and finally finish it all off with a (technically optional) tipple of bourbon.