Bake your lady fingers and let cool completely. Prepare the soaking solution by dissolving the coffee powder into the water . Once cooled , mix in the rum . Prepare the filling by beating the chilled cream to firm peaks. Keep refrigerated. In another bowl, beat the cheese, sugar and vanilla until smooth. Do not over beat or it will look curdly. Fold in about 1/4 cup of the whipped cream into mascarapone mixture (to lighten it). Fold in the remaining whipped cream. To assemble : If you plan to unmould your set Tiramisu , line your pan with plastic wrap leaving it long enough on the sides to pull out later. Dip each lady finger in the soaking solution , remove , dip the other side and place it your serving dish. You want the cookie damp but not soggy and limp. Repeat with all the cookies and line them up in your pan so that the bottom is covered. Spread about quarter cup of the filling over the lady finger layer or you can pipe it on . Repeat with another layer of lady fingers and the filling until you have used up all the lady fingers. Smooth the remaining filling on top. Cover and chill for 4 hours or longer. If serving from the pan , dust the top with sifted cocoa powder . If serving upright , place the plan upside down on your serving plate or tray. Remove the pan , remove the plastic wrap , smoothen the sides with a spatula or knife. Dust the top with sifted cocoa powder.