Line out baking tray or baking tin (20 x 30 cm) with baking paper.
Cut chocolate in chunks.
Melt chocolate chunks and butter over bain-marie. Stir every now and then.
Sieve and mix the flour, cocoa and salt.
Beat the eggs and sugar until light and creamy.
Stir the chocolate-butter mixture briefly into the egg mixture.
Fold in the flour.
Finally, carefully fold in the blueberries.
Pour into the baking tin and spread evenly.
Bake in the preheated oven at 180° C for 30 minutes.
Leave to cool completely.
Mix the mascarpone, yoghurt, powdered sugar and vanilla briefly.
Whip the cream until stiff and fold into the mascarpone.
Spread the cream over the brownies.
Decorate with blueberries and mint.
Refrigerate until ready to cut.