Sort and wash blueberries (if necessary, let frozen berries thaw). Stir cream cheese, sour cream, sugar, eggs and starch until smooth.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease square springform pan (24 x 24 cm; alternatively round, 26 cm Ø).
For the dough break chocolate into pieces. Melt with 125 g butter in pieces in a saucepan over low heat. Beat the eggs, sugar and 1 pinch of salt with the whisk of the mixer for 3-4 minutes until creamy.
Remove the chocolate butter from the stove and immediately stir into the egg mixture.
Mix flour, cocoa and baking powder. Quickly stir into the chocolate-egg mixture. Put the dough into the mould and smooth it down.
Fold the berries into the cream cheese mixture. Carefully spread them over the brownie dough. Bake in a hot oven for 40-45 minutes. Remove and allow to cool. Remove from the tin and cut into approx. 4 x 4 cm pieces.