Preheat oven to 180 C or 350 F. Grease and line a 9 x 5 - inch loaf tin with baking paper. Set aside.
To make oat flour, process oats to a fine powder.
Transfer oat flour to a large bowl.
Add cocoa powder, baking soda, ground cinnamon and salt. Whisk until just combined.
Make a well in the center of the mixture.
Add mashed bananas, eggs, and maple syrup. Fold in gently until combined.
Add ½ cup chocolate chips or chunks. Fold in again.
Pour batter into loaf tin.
Top with remaining chocolate chips or chunks.
Bake for 35-40 minutes or until a skewer inserted into the center of the bread comes out clean.
Remove from oven.
Let cool for about 10 minutes before turning on to a wire rack to cool completely.