Add the egg whites and sugar to a bowl. Using a hand mixer, whip the yolks well, until pale yellow and more than doubled in volume. This will take over 5 minutes.

Next, beat in the mascarpone cheese and vanilla extract until completely smooth and fluffy, about 1-2 minutes.

To a shallow bowl, add the coffee and liquor, if using. Mix to combine.

Ready a ceramic or glass dish with high sides.

Dip each lady finger into the coffee mixture, coating the entire cookie in coffee. Dip only for a second or two, so as to not break down the lady finger.

Layer some of the dipped lady fingers at the bottom of your dish in a single layer. Break up any lady fingers to make them fit as necessary.

Top with a fourth of your mascarpone mixture.

Next, repeat with the remaining lady fingers by dipping them in coffee and layering them over the creamy filling in a single layer. Continue for 3-4 layers.

Top with the rest of the cream and smooth it out on top.

Sift the remaining cocoa powder over the top of the tiramisu.

Cover with plastic wrap and refrigerate for at least 2 hours before serving.