Separate the eggs first for the Russian cake. Beat the egg yolks with the icing sugar and vanilla sugar until foamy. Stir in hazelnuts and baking powder, flavor with lemon zest and juice. Beat egg whites with a pinch of salt until stiff and fold in carefully.
Butter a suitable baking dish, sprinkle with breadcrumbs and pour in the mixture. Bake in the preheated oven at approx. 180 °C for approx. 45-60 minutes, depending on the size of the pan. Lift out and let cool.
Then whip the cream until stiff and sweeten with a little powdered sugar. Turn out the Russian wafers, drizzle with a little rum if desired and spread the whipped cream on top. Sprinkle with chocolate chips if desired.