Preheat oven to 350°F. Line or grease 6 cups of a muffin pan and set aside.
Grind sesame seeds using a blender or mortar and pestle. You should achieve a flour-like consistency, but it's ok if there are a few whole sesame seeds.
Mash bananas in a large bowl. Add in maple syrup, ground chia/flax seeds, milk, vinegar, and vanilla extract. Stir until well combined.
In a separate bowl, whisk together oat flour, almond flour, ground sesame seeds, baking powder, and baking soda.
Add flour mixture into wet ingredients and stir to combine. Divide batter evenly among muffin cups, filling almost to the top. Bake for 25-27 minutes, or until a toothpick inserted in the center comes out clean. Let muffins cool for 5 minutes in the pan, then transfer to a cooling rack and let them cool completely.