Step 1

Mix the black coffee, brown sugar, vodka and 3 tbsp of the Kahlúa in a shallow bowl. Mix the mascarpone in a separate bowl for 2 minutes to break it up, then beat in the double cream, icing sugar and vanilla with electric beaters until it forms soft peaks. Spoon out 1 /3 of the cream into another bowl. Mix the coffee powder with the rest of the Kahlúa and stir in to make a coffee cream.

Step 2

Dip the sponge fingers briefly into the vodka-coffee mixture, then put a single layer of the fingers in the base of a large serving dish.

Step 3

Spoon over 1 /2 of the plain cream, then finely grate over a generous layer of dark chocolate. Layer on more soaked sponge fingers, and spoon over the coffee cream then another layer of grated chocolate. Add another layer of fingers then finish with the rest of the plain cream. Chill until ready to serve, but for at least 4 hours. Dust with cocoa powder to finish.