01 - Whisk egg yolks and granulated sugar in a heatproof bowl over gently simmering water until pale and slightly thickened, approximately 3-4 minutes. Remove from heat and allow to cool briefly.
02 - Gently fold mascarpone cheese and vanilla extract into the cooled yolk mixture until smooth and fully incorporated.
03 - In a separate chilled bowl, whip cold heavy cream until stiff peaks form. Carefully fold whipped cream into the mascarpone mixture until just combined.
04 - Combine cooled espresso and coffee liqueur in a shallow dish suitable for dipping ladyfingers.
05 - Quickly dip each ladyfinger into the coffee mixture for 1-2 seconds per side. Arrange soaked ladyfingers in a single layer in a 9 x 9 inch baking dish.
06 - Spread half of the mascarpone cream evenly over the first layer of ladyfingers using an offset spatula.
07 - Add a second layer of coffee-dipped ladyfingers. Top with remaining mascarpone cream and smooth the surface evenly.
08 - Cover tightly with plastic wrap and refrigerate for at least 4 hours, preferably overnight, to allow flavors to meld and texture to set properly.
09 - Just before serving, dust generously with unsweetened cocoa powder using a fine-mesh sifter. Garnish with dark chocolate shavings if desired.