Preheat oven to 375 degrees F. Line a muffin pan with cupcake liners.
In a large bowl, make the flax egg by combining the ground flaxseed and water. Stir and set aside for 5 minutes to thicken.
In a medium bowl, add the oat flour, cacao powder, baking powder, baking soda, and salt. Whisk until well combined.
In the large bowl with the flax egg, add the ripe bananas. Mash well with a masher or fork. Add the coconut sugar, tahini, milk, apple cider vinegar, and vanilla. Whisk until well combined.
Add the dry to the wet. Stir with a spatula until combined, don’t over mix. Fold in chocolate chips. Scoop batter into the muffin pan. You want to fill the muffin tins to the top, or as much as you can.
Bake for 30 minutes, or until a toothpick inserted comes out clean. Let it cool in the pan for 10 minutes. Remove and place on a wire rack to cool completely. Enjoy! Store in an airtight container on the counter for 3-4 days. It tastes even better the next day as the flavors have more time to meld.