Preheat the oven to 350°F (175°C) and grease or line a 9x5-inch loaf pan with parchment paper.
In a large bowl, mash the bananas, then whisk in the cottage cheese, Greek yogurt, eggs, vanilla extract, and maple syrup until smooth.
Add the whole wheat flour, oat flour, baking powder, baking soda, cinnamon, and salt. Mix gently until just combined.
Fold in the dark chocolate chips or walnuts, if using.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 45-50 minutes, or until a toothpick inserted into the center comes out clean.
Cool in the pan for 10 minutes before transferring to a wire rack to cool completely. Slice and enjoy.