Preheat the oven to 180 ° C. Grease a springform pan.
Beat the butter with sugar until creamy, stir in the eggs. Then add the quark and Nutella. Stir in hazelnuts, flour and baking powder. Roughly chop the chocolate and stir in too. Pour the batter into the springform pan and put it in the oven. Bake for about 1 hour, then let cool.
Tip: If you like, you can coat the cake with couverture, chocolate glaze or hazelnut glaze.