Preheat the oven to 170°C and line a 24cm cake tin with baking paper.
Place chocolate, butter, and coffee in a bowl over a pan of simmering water.
Stir the mixture until smooth, then remove from heat to cool.
Sift flours, bicarbonate of soda, and cocoa into a bowl, then stir in sugar.
Make a well and stir in beaten eggs, sunflower oil, and milk.
Incorporate the melted chocolate mixture into the batter until combined.
Pour into the tin and bake for 60 minutes until firm.
Cool the cake completely before removing it from the tin.
Gently heat icing ingredients in a pan while stirring until smooth.
Spread cooled icing over the cake with a palette knife.