The day before or at least 4 hours ahead: melt the chocolate in a bowl set over hot water.
Separate the eggs, then whisk the yolks and half the sugar with an electric whisk until pale and stiff.
In another bowl, whisk the cream until it forms soft peaks, being careful not to take it too far. Beat the melted chocolate into the egg yolks. When cool, fold in the cream and refrigerate.
Make the coffee and, while it is hot, dissolve the remaining sugar in it. Then add the whisky or rum.
When cool, dip the sponge fingers in it briefly to moisten and arrange half to line the base of a 24 cm/9½ in spring-form tin.
Spoon over the chocolate cream and top with the remaining moistened sponge fingers. Freeze for at least 3 hours or overnight.
About 20 minutes before serving: remove from the freezer.
Dust the top with icing sugar and unclip the tin.
© 1995 Alastair Little. All rights reserved.