The mixture of homemade ladyfinger crust, cream cheese, mascarpone cheese, espresso and coffee liqueur gives tiramisu a new twist. Top with cocoa powder and grated semisweet chocolate just before serving.
Preheat oven to 350 degrees F (175 degrees C). Place a pan of water on the bottom of oven.
Line the bottom of the springform pan with parchment paper. Spread butter generously on sides of pan.
Crush ladyfingers to fine crumbs. Mix the melted butter into the crumbs. Moisten with 4 tablespoons of the coffee liqueur and 2 tablespoons espresso. Press into an 8 or 9 inch springform pan. Place in oven for 5 minutes.
In a large bowl, mix cream cheese, mascarpone, and sugar until very smooth. Add the rum and the rest of the coffee liqueur and espresso, mix. Add the eggs and the flour; mix SLOWLY until just smooth. The consistency of the mascarpone can vary. If the cheesecake batter is too thick, add a little cream. Do not overmix at this point. Pour batter into crust.
Place pan on middle rack of oven. Reduce heat to 325. Bake for 40 to 45 minutes, or until just set. Open oven door, and turn off the heat. Leave cake to cool in oven for 20 minutes. Remove from oven, and let it finish cooling. Refrigerate overnight. Right before serving, sift cocoa powder on top and grate the semi-sweet chocolate overtop.