Separate 4 eggs. Chill the egg whites. Cream 1 egg, 4 egg yolks, 200 g icing sugar, vanillin sugar and salt. Add cognac, crème fraîche and sunflower oil while stirring. Mix chestnut flour and baking powder, add bit by bit and stir in.
Beat egg whites until stiff and finally fold into the dough in 2 portions. Place in a greased springform pan (26 cm Ø), dust with flour and smooth down. Put it on a grid in the cold oven, 2nd rail from below. Switch on the oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: level 2). Bake the cake for 50-60 minutes. If necessary, cover with aluminium foil shortly before the end of the baking time. Leave the finished cake to cool in the mould on a cake rack. Coarsely chop the walnuts and almonds. Cut the cake in half horizontally with a sharp knife and sprinkle the halves with lemon liqueur. Spread the jam on the lower cake base, sprinkle with about 75 g nuts and almonds and cover with the upper cake base.
Leave the finished cake to cool in the mould on a cake rack. Coarsely chop the walnuts and almonds. Cut the cake in half horizontally with a sharp knife and sprinkle the halves with lemon liqueur. Spread the jam on the lower cake base, sprinkle with about 75 g nuts and almonds and cover with the upper cake base. Mix 250 g icing sugar, lemon juice and 1-2 tbsp. hot water. Spread the icing on the cake, sprinkle with remaining nuts and leave to dry for about 2 hours
Waiting time approx. 5 hours