Preheat oven to 350ºF (175ºC). Slide an oven rack into the center position.
In a large bowl, mash the bananas with a fork. Using a wooden spoon, mix in the yogurt, almond butter, oil, coconut sugar, egg and vanilla. Continue mixing until all the ingredients are well incorporated.
Add the oat flour, corn flour, tapioca flour, cinnamon, baking soda and salt to the wet batter and stir until no dry streaks are visible. Fold in the chopped chocolate.
Grease the 9 wells in your muffin pan with oil. You shouldn't need much more than 1/2 teaspoon per well. Distribute the batter evenly among the wells. I like using a large ice cream scoop for this.
Sprinkle a pinch of turbinado sugar and rolled oats on top of the muffins, if you like.
Bake the muffins for 25 to 28 minutes, until the edges are golden brown. Let the muffins cool in the pan for 5 minutes before transferring to a cooling rack.