Prepare the Egg Mixture: Separate the egg whites from the yolks. In a mixing bowl, whisk the yolks with 60 g of sugar until the mixture is light and fluffy.
Incorporate the Mascarpone: Lower the speed of your hand mixer and add the mascarpone cheese, one spoonful at a time, until smooth and well-combined.
Whip the Egg Whites: In a separate bowl, whisk the egg whites with the remaining 60 g of sugar until stiff peaks form.
Fold Gently: Using a spatula, gently fold the whipped egg whites into the mascarpone mixture. Be careful not to overmix to keep the cream light and airy.
Layer the Tiramisu: Dip the ladyfingers briefly into the coffee-rum mixture and place them at the base of your dish. Cover with a layer of the mascarpone cream. Repeat the process, alternating layers of soaked ladyfingers and cream until you reach the top of your dish.
Finishing Touch: Smooth the top layer and dust generously with cocoa powder.
Chill and Serve: Refrigerate for at least 4 hours, or ideally overnight, before serving.