Filling: In a large pot combine milk, sugar and vanilla sugar. Bring to boil over medium, stirring frequently to help the sugar dissolve. Remove from heat.

Add butter and chocolate into the pot. Stir well until the mass integrates.

Add ground biscuit and stir until integrated. Add walnuts and stir until well integrated. Leave to cool for 10-15 minutes.

Assembly: Carefully unwrap your tort wafer sheets. Set the best looking sheet on the side (this will be your top sheet). Take another sheet and place it on a hard surface.* Pour roughly ¼ or ⅕ of the filling in the middle of this sheet. Evenly distribute it to all sides with a knife or a spoon. Place the following wafer sheet on top of the filling and align the sides. Repeat with the filling and sheets until you are out of material. Top everything with the sheet you set aside to be the top sheet.

Wrap dessert in saran wrap. Then place a heavy object on top of it, covering the dessert as much as possible.* (a book, pan, cutting board, etc.). Leave to congeal in a cool place (or fridge) at least 6 hours, preferably overnight.

Cutting: Cut the wafer cake just before serving. Use a very sharp knife (or an exacto knife). (If you want it in shape of diamonds) Cut the cake in half (lengthwise). Then cut each half in half to get quarters. Finally, cut each quarter in half to get eights. Take an eight strip and cut diagonal lines every 4-5 blocks. Repeat with all strips.* Keep leftover cake in saran wrap in the fridge for up to 4-5 days.