Line a baking tray (approx. 35 x 40 cm) with baking paper. Separate the eggs. Beat the egg whites, 3 tbsp. cold water and 1 pinch of salt until stiff, while pouring in 125 g sugar. Fold in the egg yolks one by one.
Sift flour, starch and baking powder on top 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 10-15 minutes. Cool down.
Wash, halve and stone the nectarines. Dice 4 nectarines. Soak gelatine in cold water.
Cut the biscuit in half crosswise to make 2 smaller plates. Place each on a tray. Place a rail made of multiple-folded aluminium foil (approx. 7 cm high) around each sponge cake plate. Mix yoghurt, 75 g sugar and vanilla sugar.
Squeeze the gelatine and dissolve at low heat. Stir in 4 tablespoons of yoghurt by the spoonful, then stir into the remaining yoghurt. Chill for about 15 minutes until it begins to gel.
Coarsely grate the chocolate. Whip cream until stiff. Fold the nectarine cubes, cream and 2/3 of the chocolate shavings into the yoghurt. Spread on both sponge cake plates and chill for at least 4 hours.
Cut the yoghurt slices into about 20 pieces. Cut 3 nectarines into thin slices. Decorate the yoghurt slices with nectarine slices, remaining chocolate shavings and pistachios.