Add the powdered sugar, vanilla, one tsp rum and mascarpone cheese.
Whip until stiff peaks form.
Pour the rest of the rum into a cup of black coffee that has been cooled slightly.
Buy the small thin ladyfingers and open one package. Place the ladyfingers along the sides and bottom of a 9 inch springform pan. (a 9x13 rectangle pan works just as well with ladyfingers on bottom only).
Brush the ladyfingers with the coffee mixture. The ones on the side should only have a small amount of coffee mixture brushed on.
Now take your cream mixture and place 1/3 of the bowl over the lady fingers and carefully smooth it around the first layer of the tiramisu.
Add another layer of ladyfingers on top of the cream mixture, brush it with rum.
Now add another layer of cream mixture.
Another layer of ladyfingers and follow with the rest of the cream mixture.
Sprinkle shaved chocolate on the top and refrigerate overnight.
Unmold the pan and wrap a ribbon around it (optional) to make it look pretty.