Separate the eggs, placing the yolks in one medium bowl and the whites in a separate bowl that will allow for the egg whites to expand when whipped (medium-large bowl)
Add the icing sugar to the yolks, then mix with an electric hand mixer on medium-high speed for 2 minutes, until pale and creamy.
Fold the mascarpone into the egg yolk mixture. You don't need to be too gentle -mix until it's smooth
Swap to an whisk attachment on your hand mixer and beat the egg whites on medium speed until it reaches stiff peaks
Now fold one third off the beaten egg whites into the mascarpone mixture. Continue with the remaining egg whites, folding in a third at a time. Be careful not to overbeat it, as you want to keep the air in the mixture
Add the liqueur to your cooled coffee, then dip one lady finger biscuit at a time into the coffee mixture, then begin lining the base of your 20cm x 20cm dish with a single layer of biscuits. Continue this until you've lined the bottom of your dish (this should be half of your lady finger biscuits)
Take your mascarpone mix and spread about 1/3 of it over your lady finger biscuits.
Now make another layer of coffee-soaked lady finger biscuits
Top this with the remaining mascarpone mixture, then cover with plastic wrap and refrigerate overnight.
For best results, sprinkle your Tiramisu with a very generous layer of cocoa, followed by the grated chocolate an hour or 2 before serving, or just before transporting it.