Preheat the oven to 180°C (356°F).
Mash the bananas.
Melt the chocolate and butter together using a double boiler.
Add sugar to the melted chocolate-butter mixture and mix well.
Add the eggs and stir thoroughly.
Add the mashed bananas and vanilla extract.
Sift cake flour, baking powder, and salt together, then add them and mix.
Pour the batter into the oven pan.
Bake for about 25-30 minutes.
Once cooled, cut into pieces.