>> servings: 6
>> time: 1 hour 30 minutes plus chilling

Whisk @egg yolks{4} with @caster sugar{100%g} and @vanilla extract{1%tsp} in a #heatproof bowl{} set over a #saucepan{} of barely simmering water.

When the mixture is pale and the whisk leaves a ribbon trail when lifted, remove the bowl from the heat and set aside to cool. Whisk occasionally to prevent a skin from forming.

When the egg yolk mixture is cool, whisk in @mascarpone cheese{500%g} until thoroughly combined.

Whisk @egg whites{2} in a separate, spotlessly clean #bowl{} until they form soft peaks, then gently fold them into the mascarpone mixture.

Combine @strong black coffee{175%ml} and @rum or brandy{125%ml} in a #shallow dish{}. Briefly dip 8 of the @sponge fingers{24} in the mixture, then arrange in the base of a deep, wide #serving dish{}.

Spoon one third of the mascarpone mixture on top, spreading it out evenly. Repeat the layers twice, finishing with the mascarpone mixture. Chill for at least ~{60%minutes}.

Sift @cocoa powder{2%tbsp} evenly over the top and sprinkle with @finely grated plain chocolate{2%tbsp}. Serve immediately.