Every Italian family has their own version of this cake, which means grandmother's cake, and this is Aldo's. It's unbelievably special - well worth the effort. It makes a nice dessert for christenings and family occassions.
For the crema pasticcera pour a small cup of milk from the litre and put the rest into a saucepan with half of the sugar, lemon zest and vanillia pod and heat slowly until boiling.
In the meantime, lightly whisk the egg yolks and the pinch of salt in a bowl to break them. Sift the flour into the bowl, whisking gently and making sure that no lumps form, then whisk in the remaining sugar, and finally the remaining small cup of milk. Whisk until smooth.
By this time the milk in the pan should almost have boiled. Remove the vanilla pod and lemon zest, and then pour the milk on to the egg mixture, whisking briskly whilst doing so. Return the mixture to the heat and bring to the boil, stirring with a wooden spoon all the time. As the mixture boils it will begin to get thicker and then suddenly go very thick. At this point it is ready and you need to remove the saucepan from the heat and cool the mixture as quickly as possible. A good way to do this is to place the base of the saucepan into cold or iced water and stir the mixture gently so a skin does not form as it cools.
Now for the cake, preheat the oven to 180C and roll out the pastry and cut out a disc with a diameter of about 25cm and transfer to a baking sheet. Mix the pine nuts, raisins and rum with the crema pasticcera. Spread the mixture over the shortcrust pastry to form a dome shape. Roll out the remaining pastry large enough to cover the dome. Press the edges together and cut it neatly. Brush with the egg and pierce a few times with a folk. Bake in the preheated oven for about an hour or until golden. Remove and let it cool. Transfer to a plate. Sprinkle with vanilla sugar and serve.