Method

• 1.
  Preheat oven to 160°C. Grease and line the base of a 24 x 34cm rectangular pan.
• 2.
  Place butter and chocolate in a heatproof bowl over a saucepan of gently simmering water, stirring occasionally until melted. Sift flour and cocoa into a large bowl. Add chocolate mixture, the caster sugar, eggs and 1/2 cup water and beat until well combined. Pour into the pan and bake for 30 minutes or until a skewer inserted into the centre comes out clean. Set aside to cool.

• 3.
  Meanwhile, to make the icing, place all ingredients in a saucepan over low heat and stir until smooth and glossy.
• 4.
  Once cake is cool, spread top with icing and allow to set before cutting into 3 x 5cm rectangles. Combine icing sugar and 1 1/2-2 tablespoons warm water in a bowl until smooth.
• 5.
  Place in a piping bag and use the smallest nozzle (alternatively place in a freezer bag and make a small hole in one corner), to pipe a line horizontally across the centre of each cake, then pipe dots on each side of line to make a number; as on a domino.