Dissolve the instant coffee granules in 100 ml boiling water.

Stir in 15 ml of the Marsala wine and leave to cool in a shallow dish.

Place the egg yolk and caster sugar in a bowl and whisk until pale and thick.

In a separate bowl, combine the mascarpone with the remaining 10 ml Marsala wine.

Fold the mascarpone mixture into the egg yolk mixture.

In a clean bowl, whisk the egg white to soft peaks.

Gently fold the egg white through the mascarpone mixture until fully incorporated.

Transfer the mixture to a piping bag if desired.

Quickly dip the sponge fingers into the cooled coffee mixture, coating both sides.

Divide the soaked sponge fingers between 2 serving glasses, creating the first layer.

Pipe or spoon over half of the mascarpone mixture.

Repeat with a second layer of sponge fingers and mascarpone mixture.

Dust generously with cocoa powder.

Chill in the fridge for at least 1 hour before serving.