In a bowl, whisk together the mascarpone cheese, sugar, and vanilla extract until smooth and creamy. Be careful not to overmix.
In a separate shallow dish, combine the brewed coffee and coffee liqueur (if using).
Dip each ladyfinger into the coffee mixture for a few seconds on each side. Do not soak them for too long, or they will become soggy.
Arrange a layer of the soaked ladyfingers in the bottom of a 8x8 inch dish.
Spread half of the mascarpone mixture over the ladyfingers.
Repeat layers with remaining ladyfingers and mascarpone mixture.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or preferably overnight.
Before serving, dust the top with cocoa powder.
