1. In a pan, boil 60 ml milk with the sugar added until you obtain a thick, syrupy liquid. Add the butter and stir it into the hot milk until it melts.
2. Dissolve the cocoa in the remaining milk, add the butter-and-milk cream and boil up the mixture.
3. Crush the biscuits into small pieces and place them into a bowl. Add the raisins and pour on the hot syrup. Mix well.
4. Sprinkle powdered sugar onto a sheet of aluminum foil, and heap on the biscuit mixture. Roll the foil around it to obtain a salami-like shape. Close the ends well. Refrigerate for a day before slicing it up.