For the cardinal slice, first heat the oven to 175 degrees convection. For the snow mixture, beat egg whites and sugar until stiff and refrigerate.
For the cream, mix whipped cream, coffee and powdered sugar and also refrigerate.
For the sponge cake, beat eggs, yolks, sugar and vanilla sugar until foamy and carefully fold in flour. Now, using a piping bag, pipe 2 strips each consisting of 3 strips of egg whites onto a baking tray lined with baking paper. Fill the spaces in between with the sponge and sprinkle with powdered sugar. Bake for 20 minutes.
Whip the whipped cream and coffee mixture until stiff. Remove the baked parts from the oven and let them cool down well. Spread one part with the cream and carefully place the second part on top and refrigerate. Sprinkle the cardinal slices with a little powdered sugar before serving.