Preheat the oven to 180°C (356°F).
Sift together flour, cocoa powder, and baking powder.
Melt dark chocolate and butter using a double boiler.
Add sugar and eggs to the melted chocolate and mix well.
Add the dry ingredients and combine evenly.
Coarsely chop peanuts and fold them into the batter.
Pour the batter into the pan and smooth the surface.
Bake in the oven for 25 minutes.
Once cooled, cut into serving-sized pieces.