Grease a deep 19cm square cake pan, then line the base and sides with baking paper
Combine the butter, chocolate, sugar, water and coffee in a medium saucepan; stir over a low heat, without boiling, until the butter is just melted and the mixture is smooth.
Transfer chocolate mixture to a large bowl, allow to cool for 10 minutes.
Whisk the combined sifted plain and self-raising flours and cocoa into the chocolate mixture in two batches, then whisk in the eggs. Pour mixture into the prepared pan.
Bake in a slow oven for about 1 hour and 45 minutes.
Cover the cake pan with foil; cool cake in pan.
For the satin chocolate glaze, combine the chocolate and cream in a medium heatproof bowl, stir over barely simmering water until smooth. Spread a thin layer of glaze all over the cold cake.
Stand remaining glaze at room temperature until thickened slightly, then spread over top and sides of cold cake.
Sprinkle the top with the decorations, if desired.
Notes
This cake is best stored at room temperature for optimum texture and flavour.
