Prepare the coffee mixture: In a shallow bowl, combine the cooled espresso with the coffee liqueur (if using). Set aside.

Make the mascarpone cream: In a large bowl, whisk the egg yolks and sugar together until pale and thick, about 5 minutes. Gently fold in the mascarpone cheese until smooth.

Whip the cream: In a separate chilled bowl, whip the heavy cream until stiff peaks form.

Combine the creams: Fold the whipped cream into the mascarpone mixture in thirds, using a spatula to maintain airiness.

Assemble the layers: Dip each ladyfinger quickly into the coffee mixture and arrange a single layer in a 9x13-inch dish. Spread half the mascarpone cream over the ladyfingers. Repeat with another layer of dipped ladyfingers and the remaining cream.

Chill and finish: Cover and refrigerate for at least 4 hours, preferably overnight. Before serving, dust generously with cocoa powder and add chocolate shavings if desired.