Preheat the oven to 180°C (356°F).
Mash the banana with a fork.
In a bowl, combine the mashed banana, protein powder, oatmeal, cocoa powder, and dark chocolate. Mix well.
Add honey, baking powder, and salt if desired.
Shape the dough into cookies and place them on a baking tray.
Bake in the oven at 180°C for 12-15 minutes.
Let cool and serve the cookies on a plate.