Take egg yolks and beat them together with a sugar into a foam. Then mix in the mascarpone. On a side whip the cream and mix it into the mascarpone with foam.
Take a squared dish, spread the bottom with this cream very lightly. Then start taking biscuits, soak them quickly in a strong cooled coffee mixed together with rum so they do not soak too much and place them side by side inside the dish. Thus spread them with a layer of cream. Repeat this procedure one more time. The top gets sprinkled with cocoa powder.
Place Tiramisu to the refrigerator for about 3hrs, then you can serve.