Mix oatmeal, protein powder, baking powder, and salt in a bowl.
In a separate bowl, mash the banana and add the egg, honey, and milk. Mix well.
Combine the dry and wet ingredients to make the dough.
Add nuts and dark chocolate to the dough and mix.
Scoop the dough into balls and place them on a baking sheet.
Bake in a preheated oven at 180°C for 12–15 minutes.
Let cool before serving.