First prepare the coffee using a Moka machine big enough to serve 12 (about 3 cups) pour it in a bowl and allow to cool off, add 2 tablespoons sugar or sweeten to taste.
Mix the egg yolks with 2 ounces sugar, and mix until you obtain a creamy light mixture. Work the mascarpone in a bowl using a wooden spoon, making sure you eliminate any lumps, then add the mascarpone to the sugar-egg mixture and continue to mix well.
In a separate bowl, mix the egg whites, pinch of salt, and the remaining 2 ounces sugar, until they reach a somewhat firm, but fluffy consistency, then add them to the mascarpone mixture. Stir in the rum, if using.
Dip the savoiardi cookies (firm ladyfingers) in the coffee, and one by one lay them flat into a 7 by 11 pyrex tray, making sure you do not soak the cookies, as you want to make sure they maintain their firmness. Once the first layer of cookies has been laid out, spread a layer of the mascarpone cream on top, and dust with 1 tablespoon cocoa powder.
Now, again, prepare another layer of coffee-dipped cookies, cream and cocoa powder. Garnish the top of the cake with the shaved dark chocolate.
Cover the tray with plastic wrap and refrigerate for about 3 hours so the flavors can marry and the tiramisu can settle.
NotesCook's Note: Because you are working with raw eggs, it is mandatory that you use the freshest product you can find. Organic, free-range eggs are good enough, unless you have a neighbor with a chicken coup...in that case, get his!
Test the eggs by putting them in a bowl of water: if they fall to the bottom they are fresh and safe, if they come afloat they are ready to be tossed!
Raw Egg WarningFood Network Kitchens suggest caution in consuming raw and lightly cooked eggs due to the slight risk of salmonella or other food-borne illness. To reduce this risk, we recommend you use only fresh, properly refrigerated, clean grade A or AA eggs with intact shells, and avoid contact between the yolks or whites and the shell.