Preheat oven to 350 degrees F, line metal 9 x 5 loaf pan with parchment paper and set aside.
In a large mixing bowl, add bananas and mash with a fork or masher. Then add egg, oil, yogurt, maple syrup, vanilla extract, cinnamon, baking powder, baking soda and salt; whisk until combined.
Add oat flour and stir gently with spatula to combine. Add walnuts, 1/2 cup chocolate chips and stir a few times.
Pour batter into previously prepared loaf pan, add remaining 1/4 cup chocolate chips on top and bake for 60-65 minutes or until the toothpick inserted in the middle comes out clean.
Remove oat flour banana bread from the oven and let cool off for 10 minutes. Then remove bread from a loaf pan, transfer to a cooling rack and let it cool for another hour or so.
Slice with serrated knife, it works best with breads to keep them from falling apart.
Notes
Store: Store bread in an airtight container in a cool dry place for up to 3 days. After refrigerate for another 3 days.
Freeze: Bake and cool completely. I recommend to freeze bread unsliced to retain moisture. Place in a gallon size Ziploc container, let out as much air as possible and seal. Freeze for up to 3 months. Thaw on a counter for a few hours.