Preheat oven to 320 °F (160 °C).

For batter I, beat egg whites to stiff peaks with granulated sugar.

For batter II (sponge cake), beat eggs, egg yolks, granulated sugar, and vanilla sugar until creamy.

Carefully fold in the flour.

Set out 3 sheets of parchment paper (about 8in (20 cm) wide).

Using a piping bag fitted with a large round nozzle, pipe 3 stripes of egg whites onto each paper, leaving space between the stripes.

In between, pipe two strips of cake batter.

Do not spread the batter out.

Dust with confectioner’s sugar and bake for 35 minutes.

Let cool and carefully pull off the paper.

For the filling of your choice, whip the cream.

For variation I, flavor the cream with vanilla sugar, spread redcurrant marmalade on the first layer and whipped cream on top of that.

Place the second cake layer on top, spread with redcurrant marmalade and whipped cream again, and then place the last cake layer on top.

For variation II, flavor the whipped cream with confectioner’s sugar and instant coffee and then follow the directions as in variation I.

Before cutting, dust with confectioner’s sugar.