1 Gather and measure out all of the ingredients.
2 Grease the bottom of a springform pan or line with parchment paper.
3 Beat the yolks with half the sugar and the vanilla sugar until fluffy. Beat the egg whites into a meringue and sprinkle in the remaining sugar before it becomes quite stiff. Then continue stirring until the meringue becomes stiff. Fold the egg whites with a mixing spoon into the egg yolk mixture.
4 Mix the flour with the cornstarch, sift it over the egg mixture and then fold it in. Pour the batter into the prepared springform pan, smooth the surface and bake on the middle rack in a preheated oven (175°C, approximately 350°F) for 25-30 minutes (until a toothpick inserted into the center comes out clean).
5 Remove the cake from the oven, and let cool slightly. Use a thin knife to remove the edges from the springform pan, and lay on a wire rack. Cool and let rest for at least 2 hours. Then cut twice horizontally. Place one layer into a cake ring.
6 For the first filling, dissolve the gelatine in cold water. Warm the whiskey and sugar slightly. Squeeze out the gelatine well and dissolve in the warm liquid. Let cool down. Whip the cream. Once the whiskey starts to solidify, fold in the cream, and spread the cream onto the bottom layer. Place on the next layer and press lightly.
For the second filling, beat the cream, cream stabilizer and sugar until stiff. Stir the espresso with 2/3 of the cream and spread this cream on top of the second layer. Place the third layer on top and press lightly. Coat the cake around and on top with the rest of the remaining cream filling. Refrigerate. Melt chocolate in a warm water bath, fill into a parchment bag, cut off a small tip and pipe a fine grid pattern onto the cake. Decorate the edge of the cake with chocolate curls. Chill until ready to serve.