Preheat oven to 325 degrees Fahrenheit. Line a 9″ x 5″ loaf pan with parchment paper, leaving some to overhang the sides.
Mash the bananas in a large bowl, leaving a few chunks.
Beat the peanut butter and eggs into the banana mixture. Add the coconut sugar, arrowroot powder, vanilla extract, baking soda, baking powder, and fine grain sea salt, and stir until well-combined. Add the apple cider vinegar and stir until well incorporated. Stir in the chopped chocolate, leaving a small handful out to sprinkle over the top of the bread.
Pour the batter into the prepared loaf pan. Sprinkle the top of the bread with reserved chocolate chunks and flaky sea salt, if using.
Bake for 50 – 60 minutes, or until a toothpick in the center comes out completely clean. Allow to cool for at least 20 minutes in the pan before removing. Store for up to 4 days in the fridge, or slice and keep in the freezer for up to 6 months, toasting a slice at a time when you’re ready to eat!