Whisk butter and 250 g sugar with the whisk of the hand mixer until foamy. Stir in the eggs one after the other. Mix flour and baking powder and stir in briefly. Spread half of the dough on a greased baking tray (38 x 34 cm). Stir cocoa into the remaining dough and carefully spread it on the light-coloured dough. Drain the apricots well and spread them evenly on the dough, except for 8-10 halves for decoration.
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 35 minutes. Let them cool down. In the meantime soak the gelatine. Whip the cream until stiff and allow vanilla sugar to trickle in. Mix yoghurt and 50 g sugar. Dissolve the gelatine and stir into the yoghurt drop by drop. As soon as the cream starts to gel, fold in the cream and spread on the cake. Cool until the cream is firm. Coarsely chop the chocolate coating and melt on a hot water bath. Allow to cool slightly while stirring. Pour the couverture into 1 disposable piping bag, cut a small opening and spray a grid on the cake. Cut the rest of the apricots into slices and spray lines onto them.
As soon as the cream starts to gel, fold in the cream and spread on the cake. Cool until the cream is firm. Coarsely chop the chocolate coating and melt on a hot water bath. Allow to cool slightly while stirring. Pour the couverture into 1 disposable piping bag, cut a small opening and spray a grid on the cake. Cut the rest of the apricots into slices and spray lines onto them. Let the chocolate coating set. Cut the cake into 42 squares and decorate with apricot slices
waiting time approx. 1 1/4 hours