In a small bowl add cocoa powder and boiling water and mix everything well. Let aside to cool.
Carefully separate the egg whites from the yolks, remembering that to whip the egg whites well they must not contain any trace of yolk. Then whip the egg yolks with a hand mixer, pouring in only half of the sugar.
As soon as the mixture has become clear and frothy, and with the mixer still running, you can mascarpone cheese, slowly. When the cheese is incorporated, you will have obtained a thick and compact cream; set it aside.
Clean the mixer attachments very well and beat the egg whites, pouring in the remaining sugar a little at a time. Whisk them into stiff peaks; you will know they are ready if the mixture does not move when you overturn the bowl.
Take a spoonful of egg whites pour it into the bowl with egg yolks and sugar and stir vigorously with a spatula, to thin the mixture. Then proceed to add the remaining egg whites, slowly, stirring very gently from bottom to top.
Once ready, grab a 33x23cm baking tray (glass preferably). Add the Cointreau to cocoa and water mixture. Then soak the ladyfingers for a few moments in the cooled chocolate (make sure the ladyfingers are quite soft) first on one side and then the other.
Arrange the soaked ladyfingers inside the tray, side by side, to create the first layer, over which you will spread part of the mascarpone cheese cream.
Make sure to level it carefully so that you have a smooth surface. Continue to arrange the chocolate-soaked ladyfingers, then add another layer of cream.
Level the surface, sprinkle it with cocoa powder, some chopped pecans, and allow it to set in the fridge for a couple of hours.