Line a baking tray (approx. 35 x 40 cm) with baking paper. Separate the eggs. Beat the egg whites and 1 pinch of salt until stiff, adding 75 g sugar and vanillin sugar. Beat the egg yolks separately into the mixture. Sift the flour, starch and baking powder into it and fold in. Spread on the baking tray. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for 10-12 minutes
Warm up the jam, mash it. Turn sponge cake onto a damp tea towel. Remove baking paper immediately. Spread the sponge cake with jam, roll up from the long side. Cooling down
Cut the sponge roll into about 16 slices. Place the springform pan rim (26 cm Ø) on a cake plate. Place approx. 9 slices close to each other on the rim of the cake tin. Rest slices side by side in the middle
Soak gelatine in cold water. Drain the mandarins and collect the juice. Heat 100 ml juice (do not boil!). Squeeze out the gelatine and dissolve it while stirring. Stir in champagne. Mix mascarpone and 75 g sugar. Stir in the champagne mixture. Whip cream until stiff. Fold cream first, then mandarins into the champagne cream. Spread on the base. Chill for approx. 3 hours