Preheat oven to 350 degrees F. Line a loaf pan with parchment paper.
In a large bowl, make the flax eggs by combing the ground flaxseed and water. Stir and set aside for 5 minutes to thicken.
In a medium bowl, add the oat flour, almond flour, baking soda, baking powder, cinnamon, and salt. Whisk until combined.
In the bowl with the flax eggs, mash the ripe bananas. Then add the vanilla, coconut oil, maple syrup, and apple cider vinegar. Whisk until well combined.
Add the dry ingredients into the bowl with the wet. Stir with a spatula until just combined. Don’t overmix! Pour 1/3 of the batter into a different bowl. In a small bowl, stir together the cacao powder and hot water. Add it to the bowl with 1/3 batter. Stir until combined. Fold in chocolate chips to the chocolate batter.
Pour 1/3 of the plain batter into the lined loaf pan. Then pour 1/2 of the chocolate batter into the pan on top of that layer. Add the next 1/3 of the plain batter followed by the last half of the chocolate batter. Finally add the last 1/3 of the plain batter on top. Gently swirl (making an “S” shape) with a butter knife a few times (don’t go overboard or else you won’t see your swirls once baked). Top with extra chocolate chips.
Bake for 60-70 minutes, or until a toothpick inserted comes out clean. Let it cool in the pan for 15 minutes. Then transfer bread to a cooling rack to cool completely. Enjoy!