Separate the egg whites and yolks into two large bowls. Whisk the whites until stiff. Add the sugar to the yolks and whisk again (no need to clean first) until thick and foamy – this will take about 5 mins. Whisk the mascarpone and Baileys into the egg yolks until you can’t see any streaks of cheese. Carefully fold the whites into the mascarpone mixture with a large metal spoon to keep in as much air as possible.

Get your serving dish ready (ours was 20 x 15 cm). Pour the coffee into a shallow dish and dip in a few sponge fingers at a time, turning them for a few seconds until they are nicely soaked, but not soggy. Layer these into the dish until you have used half the biscuits, then evenly spread over half of the creamy mixture. Using the coarse side of the grater, grate over most of the chocolate, then repeat the sponge and cream layers (you should use up all the coffee). If you want a pretty finish, you can pipe on the final cream layer.

Cover and chill for a few hours or overnight. This can be kept in the fridge for up to two days. To serve, dust with cocoa powder and grate over the remaining chocolate.