Separate the eggs whites and yolks.
mix the yolks with the sugar until creamy and white looking. at this point add the cognac and continue to mix. as soon as the cognac is completelly mixed, add the mascarpone cheese, that has been worked before with a wood spoon to make it softer.
now mix the eggwhites untill solid, once the eggwhites are solid, pour the mascarpone cheese cream into and mix the two with a wood spoon.
once the mix is smooth, start to assamble the tiramisu laying down a first layer of ladyfingers, cover them with the cream before preparred, and then top with cocoa.
keep doing layers until the ingridients are finished.
put the pan in the fridge and let it rest about 3 hours before serving it.