Steps
In a bowl, whisk together the egg yolk and sugar until creamy.
Gently fold in the mascarpone cheese until smooth.
In a shallow dish, combine the cooled espresso with the coffee liqueur (if using).
Dip each ladyfinger briefly into the espresso, ensuring they are soaked but not soggy.
Layer half of the soaked ladyfingers in a small serving dish.
Spread half of the mascarpone mixture over the ladyfingers.
Repeat with the remaining ladyfingers and mascarpone.
Cover and refrigerate for at least 2 hours to set.
Before serving, dust with cocoa powder on top.