Preheat oven to 350F/175C.
Line a 12 cup muffin tray with parchment liners.
Spray with non-stick spray if you are using regular paper liners or it will stick.
In a large bowl, combine masged banana, sugar, yogurt, vanilla extract and eggs.
Mix to combine.
In a separate bowl, combine oat flour, wholewheat pastry flour, baking soda, baking powder, cinnamon, and salt. Whisk to combine.
Add dry ingredients to wet ingredients in 3 batches.
Mix until just combined.
Fold in ¼ cup crushed walnuts and ¼ cup mini chocolate chips.
Fill muffin cups to 3/4 full.
Top each muffin with remaining chocolate chips and walnuts.
Bake 15-18 minutes, or until toothpick inserted comes out clean.