First, prepare the syrup. To do this, boil water with sugar. Add the raisins and fruit schnapps and leave to infuse overnight.
For the light sponge cake, beat the yolks with 20 g granulated sugar, vanilla sugar, a pinch of salt and lemon zest until foamy. Beat egg whites and remaining granulated sugar until semi-stiff. Carefully mix with flour into yolk mixture and spread 6 mm thick on prepared baking sheet (40 x 35 cm) and bake in preheated oven at 180 °C for about 8 minutes until light brown.
For dark sponge, beat eggs with water, granulated sugar, vanilla sugar and pinch of salt until foamy. Add the oil using a hand blender without air (place the blender on the bottom). Mix cornstarch, flour and cocoa powder and gently add to the egg mixture. Spread 6 mm thick on prepared baking sheet and bake in preheated oven at 180 °C for 8 minutes.
For the cream, soak gelatine in ice-cold water. Mix cream, milk, water, granulated sugar, vanilla sugar and salt, bring to the boil and add vanilla pudding powder. Dissolve soaked gelatine in it and stir until cold.
To finish, prepare 2 casseroles of about 20 x 15 cm each. Use the casserole dish as a template and cut out 2 oval slices of each type of sponge cake together with the baking paper.
Put in the first light sponge layer, remove the paper and brush well with syrup. Pour in about 5 mm of cream and sprinkle squeezed raisins (from the syrup). Add a handful of walnuts crushed in your hands.