01 - Whisk egg yolks and sugar together in a heatproof mixing bowl over a pot of gently simmering water (bain-marie) until pale and slightly thickened, approximately 3–4 minutes. Remove from heat and allow to cool slightly.
02 - Gently fold mascarpone cheese and vanilla into the cooled yolk mixture until smooth and creamy. Ensure no lumps remain.
03 - In a separate chilled bowl, whip heavy cream to stiff peaks. Carefully fold the whipped cream into the mascarpone mixture until just combined. Avoid overmixing to maintain airy texture.
04 - Combine espresso and coffee liqueur in a shallow dish wide enough for dipping ladyfingers.
05 - Quickly dip each ladyfinger into the coffee mixture for 1–2 seconds per side. Do not soak; ladyfingers should remain firm to prevent soggy texture.
06 - Arrange a single layer of soaked ladyfingers in a 9 x 9 inch dish. Spread half of the mascarpone cream evenly over the ladyfingers using a spatula.
07 - Add a second layer of dipped ladyfingers. Top with remaining mascarpone cream and smooth the surface evenly.
08 - Cover the dish and refrigerate for at least 4 hours; preferably overnight for best texture and flavor development.
09 - Just before serving, dust generously with unsweetened cocoa powder using a sifter. Sprinkle with dark chocolate shavings if desired. Cut into squares and serve chilled.