At the beginning, we brew bitter coffee, cool it down, and then pour it into a container.
Separate the egg yolks from the egg whites. Beat the egg whites until stiff peaks form. Whisk the egg yolks with sugar until the sugar completely dissolves. Add rum and mascarpone to the egg yolks and gently fold in the previously prepared egg whites.
Take a large enough dish and arrange the biscuits in it. Dip the biscuits in coffee according to preference until completely soaked. Cover the biscuits with the cream and then place another layer of biscuits. Repeat the process.
Smooth out the final layer of cream and sprinkle cocoa powder on top through a sieve.
For an even better flavor, prepare tiramisu one day in advance.