Combine mascarpone and egg yolks. Whisk egg whites and fold into mascarpone mixture. Do not over-beat as it will curdle.
Mix coffee and liqueur together and dip sponge fingers.
Put one layer of sponge fingers into a shallow dish that is suitable for serving.Then top with a layer of the mascarpone mixture and grated chocolate.
Repeat with sponge fingers, mascarpone and chocolate. It is best made the day before but refrigerate at least 3 hours before serving. It will keep for up to 1 week – refrigerated. The most popular liqueurs to use are Kahlua, Sambucca, Tia Maria or Peppermint Essence.