Preheat your oven to 350°F (180°C) and prepare a 20 cm (7.9 inches) loaf pan by lining it with parchment paper or greasing it with oil.
In a large mixing bowl, mash three ripe bananas using a fork until completely smooth. Incorporate nut butter and eggs into the mashed banana mixture until fully combined.
Add your choice of granular sweetener, vanilla extract, and sea salt to the wet mixture. Whisk or stir with a fork for about two minutes until everything is well blended.
Stir in oat flour (or oat flour plus protein powder), cocoa powder, and baking powder into the wet mixture. Mix thoroughly until all ingredients are well combined before folding in the chocolate chips.
Pour the batter into your prepared loaf pan. If desired, sprinkle additional chocolate chips on top before placing it in the oven to bake for 30 to 40 minutes or until a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and allow it to cool in the loaf pan for about 15 minutes. Carefully take it out of the pan and let it cool completely before slicing into delicious servings.