Grind the oats finely to make oat flour.
Mix the oat flour with cocoa powder and baking powder.
Mash the banana and combine with eggs, milk, and honey to make the batter.
Mix the dry ingredients with the liquid batter.
Chop the dark chocolate and add it to the batter.
Lightly coat a pan with cooking oil and pour in the batter.
Bake in a preheated oven at 180°C for 25–30 minutes.
Cool the finished cake before eating.