First, preheat the oven to 190 °C top/bottom heat or 160 °C convection oven.
Cover a springform pan with baking paper and grease the sides.
Coarsely chop the chocolate and melt over a water bath.
Beat the butter, powdered sugar and egg yolks with the whisks of a mixer until creamy. Stir in almonds, flour and chocolate.
Whip egg whites until stiff and gently fold in.
Pour the batter into the prepared pan, top with 2/3 of the blueberries and bake for about 30 minutes.
Then sprinkle the remaining blueberries and granulated sugar on top and bake the cake for another 10 minutes.