First, beat the yolks with the powdered sugar until they increase in size 3-4 times. Add the mascarpone and stir gently.
Beat the egg whites into hard snow. Then add them to the mascarpone and mix gently. Add the brandy or rum to the prepared espresso. Dip the biscotti one by one into the coffee mixture and arrange them side by side in the tray.
Above each row of biscotti, smear on a row of cream. Top with dipped biscotti and cream again. The topmost layer needs to be cream.
Put the dessert in the refrigerator overnight. Before serving, sprinkle with cocoa and a little powdered sugar.