Whisk egg yolks and sugar together until pale, thick, and creamy.
Gently fold in mascarpone cheese and vanilla extract until smooth.
Whip heavy cream with a pinch of salt until stiff peaks form.
Slowly fold whipped cream into the mascarpone mixture to keep it light and airy.
Quickly dip each ladyfinger into room temperature coffee and arrange in a 9x13 dish in a single layer.
Spread half the mascarpone mixture over the ladyfingers and smooth it flat.
Add another coffee-dipped ladyfinger layer on top and cover with remaining mascarpone mixture.
Cover the dish and refrigerate for at least 4 hours or overnight.
Dust with cocoa powder before serving.
Notes
For a lighter version, substitute whipped egg whites for the cream. Chill overnight for best texture. Store leftovers in sealed container up to 3 days.