Line the bottom of a springform pan (26 cm Ø) with baking paper. Beat the eggs, 100 g sugar, vanilla sugar, salt and 1 tbsp lukewarm water for approx. 8 minutes until fluffy. Sift flour and baking powder on top and fold in. Brush into the mould. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/gas: level 2) for about 20 minutes. Cooling down
Separately soak 6 gelatine leaves in cold water. Halve the sponge cake 1x. Close the cake ring (at least 7 cm high) by 1 base. Spread 3-4 tbsp. jelly on top. Place 2nd cake base on top
Whip the cream until stiff. Squeeze 6 gelatine leaves, dissolve at low heat. Stir in strawberry yoghurt by the spoonful. Squeeze 6 gelatine leaves and dissolve. Stir in vanilla yoghurt by the spoonful. Fold half the cream into the strawberry yoghurt, the rest into the vanilla yoghurt. Chill both creams until they start to gel. Spread the vanilla cream on the middle of the sponge cake, spread the strawberry cream around it. Smooth everything out. Chill overnight.
Wash, clean and halve or quarter the strawberries. Cover the cake with them. Mix icing powder and 1 tablespoon of sugar. Stir in 1/4 l water, bring to the boil while stirring. Spread on the strawberries. Chill for about 30 minutes.
Warm the rest of the jelly. Spread the bottom edge of the cake with the jelly and sprinkle with brittle