Preheat the oven to 180°C (356°F).
Finely grind whole almonds into powder.
Mash the banana and mix well with the egg.
Add almond flour, cocoa powder, and baking powder, and mix evenly.
Pour the batter into the mold and smooth out the top.
Bake in the 180°C oven for 20–25 minutes.
Let cool before serving.