In a small bowl, combine 1/3 cup granulated sugar with 1/2 teaspoon of the vanilla extract. Set aside.
In a separate bowl, whip the egg yolks into the sugar-vanilla mixture until pale and thick.
In another large bowl, using an electric mixer, beat egg whites until stiff peaks form.
Gently fold the mascarpone cheese into the egg yolk mixture until fully incorporated and smooth.
Carefully fold the stiffly beaten egg whites into the mascarpone mixture until light and airy.
In a separate shallow dish, pour the cooled brewed coffee. Quickly dip each ladyfinger halfway into the coffee to moisten without soaking (about 1 second per side). Avoid over-saturation.
Layer a ladyfinger into each serving cup, followed by a spoonful of mascarpone cream. Repeat for a second layer.
Chill the cups in the refrigerator for at least 4 hours or overnight to allow the flavors to meld and the layers to set.
Before serving, dust the tops lightly with cocoa powder or a sweetened coffee powder if desired.