Mash the banana and place it in a bowl.
Add the egg, melted butter, and sugar, then mix well.
Sift in the cocoa powder and flour.
Add the chocolate chips and combine the batter evenly.
Pour the batter into a mold and smooth the surface.
Bake in an oven preheated to 180°C for 20-25 minutes.
Let it cool, then cut into bite-sized pieces.