175g/6oz caster sugar
25g/1oz cocoa powder, sieved, plus extra to dust
icing sugar, to dust
180²µ/6¼´Ç³ú dark chocolate (about 40% cocoa solids), broken into pieces
300²µ/10½´Ç³ú dark chocolate, broken into pieces
knob of butter, for greasing
150³¾±ô/5½´Ç³ú double cream, whipped to soft peaks
300ml/½ pint double cream
6 free-range eggs, separated
2 tbsp whisky