For the dough, grease a baking tray (approx. 35 x 40 cm) and dust with flour. Put flour, sugar, vanilla sugar, 1 pinch of salt, eggs and 375 g butter in pieces in a mixing bowl. Knead everything first with the dough hooks of the mixer and then briefly with your hands to a smooth dough.
Press the dough on the baking tray with your hands to a flat base. Then prick several times. Put in a cool place for about 30 minutes. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 20-25 minutes.
Allow to cool on the tray.
For the toffee cream, bring butter, syrup and cream to the boil in a saucepan while stirring. Boil down at medium heat while stirring several times for 25-35 minutes until the mixture has a golden brown colour. Spread the toffee cream on the baked base.
Place in a cool place for about 1 hour.
Break chocolate into pieces for the chocolate icing. Melt with whipped cream and white fat at low heat while stirring. If necessary, let it cool down a little and put it in a cool place until the icing is a little thicker.
Spread on the toffee cream. Put in a cool place for about 1 hour. Cut the shortbread into pieces. Store in a cool place so that the chocolate layer does not become soft.