Preheat the oven to 180 C. Place a pan of water on the bottom of oven.
Crush the sponge fingers into fine crumbs. Mix the melted butter into the crumbs. Moisten with 2 tablespoons of Tia Maria. Press into a 20 or 23cm cheesecake pan with a removable base.
In a large bowl, mix cream cheese, mascarpone and sugar until very smooth. Mix in remaining Tia Maria.
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 the mixture onto the crust.
Place pan on middle shelf of oven. 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 for at least 3 hours, or overnight, before serving.