Sheets: Keep the ingredients at room temperature for a few hours.
In a bowl, rub the lard with a pinch of salt and sugar. Add one egg yolk, mix with a fork until you incorporate them all. Add the milk. We mix the flour with the baking powder and we add it, we mix it initially with a whisk, then we knead by hand until we obtain a dense, non-sticky dough. Divide the dough into 3 equal portions. We spread directly on the baking sheet, one sheet at a time, prick it with a fork from place to place, then put it in the oven, in the oven, over medium heat, for about 10-12 minutes. We take them out and leave them to cool.
For the cream, rub the soft butter with the sugar and cocoa. Add milk and rum, mix. Add the jam, walnuts and then crumble a sheet and biscuits. Put over the composition of the bowl and mix with a spatula, until you get a not very soft paste.
In a tray, place a baking sheet, place a sheet of cake, spread the cream and then level nicely. Place the second sheet of cake and press lightly to place evenly on the cream. Put another baking paper on top, place a wooden chopper on top and let the cake cool, while we prepare the meringue.
For meringue, mix the egg whites in a bowl to be placed on a steam bath. When the foam becomes white and dense, add the powdered sugar and continue mixing. We move the bowl on the steam bath and let the meringue cook for about 30 minutes, mixing from time to time. When the meringue hardens on the edges of the bowl, take it from the steam bath and spread it over the cake.
Let it cool a bit, sprinkle with chocolate flakes and then let the cake cool until the next day.