Soak the black beans and blend them until smooth.
Melt dark chocolate and butter together over a double boiler.
Mix the beans, melted chocolate, sugar, eggs, and vanilla extract.
Sift in the flour, baking powder, and salt, then quickly combine.
Pour the batter into the mold and spread evenly.
Bake in a 180°C oven for 25 minutes.
Once cooled, cut into serving-size pieces.