Mix all ingredients of the basic batter for 3 minutes at fast speed with a flat beater, then spread evenly on a baking tray of 60x20cm. Bake for 25-30 minutes at 180°C. After cooling down, spread the chopped strawberries on the cake.
Then, mix all ingredients for the creme topping at fast speed with a fine-wired whisk for 4 minutes, spread 1500g evenly on the cake. Fill the rest in a piping bag and pipe long strains with a small round nozzle across the cake. Spread the jam and top up with white chocolate shavings before refrigeration.