1 teaspoon of cocoa powder
1/6 cups melted butter
1/2 cups of icing sugar
2 tablespoons of strong espresso coffee
Mix the melted butter and the swifted icing sugar, and add the espresso and cocoa. Beat with a fork until smooth.
The icing should not be too liquid or it will not stick to the cake - if it is, add a teaspoon or so of icing sugar and stir again.