Add the butter to a medium-sized pan, add the chocolate in large chunks and allow to melt over a medium heat. Allow the mixture to cool slightly. Fold the whisked eggs, one after the other, into the chocolate mixture and mix together. Next, mix in all the remaining ingredients including Hermesetas Granulated, then stir well. Pour into a well-greased or parchment paper-lined square baking tray (20 x 20 cm) and smooth out.
Bake at 180°C for 10 minutes. Allow to cool slightly, then cut into 2 x 2 cm cubes. Once cooled, dust with icing sugar.