1.Preheat oven to 160°C (140°C fan forced). Grease 23cm-square slab pan, line base and sides with baking paper, extending paper 5cm above sides.
2.Combine butter, chocolate, sugar, the water, whisky and coffee in medium saucepan, stir over low heat until mixture is smooth, cool. Stir in sifted flours and cocoa then egg.
3.Pour mixture into pan, bake about 1¼ hours. Stand 10 minutes then turn, top-side up, onto wire rack to cool. Cut into nine pieces, serve dusted with sifted icing sugar, if desired.