Preheat the oven to 180°C (356°F).
Mash the bananas with a fork.
Add protein powder, oatmeal, and cocoa powder to the mashed bananas and mix well.
Chop the dark chocolate finely and mix it into the dough.
Shape the dough into rounds and place them on a baking sheet.
Bake in the oven at 180°C (356°F) for 12-15 minutes.
Let cool and serve.