Coarsely chop the hazelnuts. Cream fat, 200 g sugar, vanillin sugar and salt. Add the eggs one after the other. Mix flour, starch, 100 g chopped nuts, cinnamon and baking powder. Alternately stir cream into the egg-fat mixture.
Grease the grease pan of the oven (38x32 cm) and spread the dough evenly on it. Sort the blueberries and wash and dab dry if necessary. Sprinkle on the dough. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 30 minutes. Let the finished cake cool down in the fat pan. Caramelise 100 g sugar in a pan. Add 50 g nuts. Pour onto baking parchment and allow to cool. Chop the brittle roughly.
Let the finished cake cool down in the fat pan. Caramelise 100 g sugar in a pan. Add 50 g nuts. Pour onto baking parchment and allow to cool. Chop the brittle roughly. Cut cake into 24 pieces, sprinkle with brittle and serve