Prepare the shortcrust: Mix together flour, salt, cacao powder and sugar. Then cut the butter into smaller chunks and add together with the egg to the dough. Knead until smooth, wrap into plastic and put in the fridge for 30 minutes.

Meantime prepare the filling by separating the eggs and beat the egg whites until stiff. In another bowl mix together sugar, ricotta, mascapone, cottage cheese and the yoghurt. One after another add the egg yorks. Over an waterbath melt the dark chocolate and nut nougat and slowy add to the mixture. Now add cacao powder and the chocolate custard powder. At last add the stiff egg whites.

Preheat oven to 180°C and prepare a pan by oling it. Take the shortcrust dough out of the fridge and half it. Roll out and put into the pan, cover with caramel sauce. Then take the other half and roll in out the same way. Put it onto the caramel sauce and try to form a edge to prevent filling from leaking.

For the streusel: Whisk together flour, sugar, salt and cacao powder. Melt butter and add it with the cold water. Crumble dough until streusel are appearing. Cover the cake with the streusel and bake for one hour. Let it cool completely then remove from pan.