Let the blueberries thaw slightly. Chop the chocolate. Cut butter into pieces. Roughly chop the nuts. Melt the chocolate and butter in a pot at low heat
Beat 2 eggs, brown sugar and salt in a bowl with the whisk of the hand mixer until creamy. Remove the chocolate-butter mixture from the heat and stir in. Mix flour, cocoa, nuts and baking powder and fold into the chocolate mixture. Put about 2/3 of the dough into a greased springform pan (26 cm Ø) and smooth it down
Stir curd, sugar, 2 eggs and starch with a whisk until smooth. Fold blueberries into the quark mixture. Carefully add the quark to the dough and spread. Spread the rest of the dough in patches. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 45 minutes. Take out and let cool on a cake rack
On 16 pieces: