Separate eggs. Beat the egg whites and 2 tablespoons of water until stiff, add 100 g sugar and 1 sachet of vanilla sugar. Fold in egg yolks one after the other. Mix flour, 25 g starch and baking powder, sieve onto the egg mixture and fold in
Line the bottom of a springform pan (26 cm Ø) with baking paper. Fill in the sponge cake mixture and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 20 minutes, remove from oven and let cool down for at least 2 hours
Clean, wash and cut the rhubarb into small pieces. Bring the nectar and 25 g sugar to the boil in a pot, add the rhubarb. Cover and simmer for 3-4 minutes. Stir approx. 25 g starch with 2-3 tbsp. water until smooth. Pour into the rhubarb while stirring, bring to the boil again and simmer for 1 minute, remove from heat
Remove the base from the mould and cut in half horizontally. Place a cake ring around the lower cake base and spread rhubarb compote on top. Cover with the second cake base, let it set overnight
Remove the cake from the ring. Soak the gelatine in cold water. Mix the sour cream, 1 packet of vanilla sugar and 50 g of sugar. Whip the cream until stiff. Squeeze the gelatine, dissolve, stir in 2-3 tbsp. sour cream, stir into the remaining sour cream. Fold in the cream. Spread the sour cream loosely on the cake, chill for about 1 hour. Sprinkle the pistachios over the cake
waiting time approx. 15 hours
Picture 02: Ground pistachios on the edge of the sour cream