Bake each sheet of puff pastry in a tray in the oven. Once the sheets become nice and red, take them out and allow to cool. Divide each sheet using a knife into separate sheets - 2 sheets give you 4 total (or more). Prepare the pudding according to the package directions, dissolve it in part of the milk and add to the boiled milk and sugar.
Add the rum essence and stir until thickened. Leave the finished pudding to cool completely (at room temperature). Beat the soft butter into a fluffy and smooth cream with a mixer for an extended amount of time. The pudding and butter must be at the same temperature, otherwise the cream will not form well.
Add the cooled pudding to the butter in portions and beat until you get a homogeneous buttercream. Bind the individual puff pastry sheets with this cream. Sprinkle each one with raisins and a little splash of rum, then cream and crushed nuts on top.
Brush the top of the cake with plenty of cream and make decorations as desired. Put it in the refrigerator for 1 night / day before serving.