Grease an 8x8 baking dish with butter or coconut oil. Preheat oven to 350 degrees.
Melt the coconut oil and chocolate chips in a medium bowl. Stir until well combined.
Add the mashed banana, salt and vanilla and whisk together.
Whisk in the eggs one at a time.
Add both flours and stir until just combined.
Transfer the batter to the skillet, top with additional chocolate chips if desired and bake for 20-22 minutes until the edges start to pull away from the sides and the middle is still just slightly undercooked.