In a mixing bowl, pour in the heavy whipping cream and beat it on medium speed. Gradually add the granulated sugar and vanilla extract, and whip until stiff peaks form (3-5 minutes).

Gently fold the room-temperature mascarpone cheese into the whipped cream until no lumps remain.

In a shallow dish, brew a strong cup of cold espresso and cool completely. Mix in liqueur if using.

Quickly dip each ladyfinger into the espresso mixture for about 1 second, then arrange them at the bottom of an 8x8 inch dish.

Spread half of the mascarpone mixture evenly over the layer of ladyfingers.

Repeat layering with another round of dipped ladyfingers followed by the remaining mascarpone mixture on top.

Smooth the top, dust with cocoa powder, cover with plastic wrap, and refrigerate for at least 3-4 hours or overnight.