In a deep dish, make two double expressos and add the whiskey (optional). Set aside, allowing the coffee to cool down.
Separate yolks from whites. With an electric mixer, beat egg whites until they're firm, gradually adding 1,7oz | 50g of sugar and continue to beat until soft peaks form. Set aside.
In another bowl, whisk egg yolks with the rest of the sugar (3,6oz | 100g), until you get a fluffy, white cream. Add the mascarpone cheese and mix well until it bubbles and you get a creamy consistency.
With a spatula, gently fold the whisked egg whites into the previous preparation.
Quickly dip half of the ladyfingers into the coffee mixture, placing them on the bottom of an oven dish.
Cover with half of the mascarpone mixture. Dip the rest of the ladyfingers an place them on top.
Finish with the rest of the mixture and refrigerate for at least 6 hours - ideally 12 (the longer it stays in the fridge, the better it will be).
Dust with cocoa powder before serving.