Preheat oven to 350℉. Line an 9x5 inch loaf pan with parchment paper.
In a large bowl, whisk together your mashed bananas, butter and syrup until smooth. Next, whisk in the eggs and vanilla. Sift in the flour, cacao powder, baking soda, salt, espresso powder and mix until just incorporated - DO NOT OVERMIX. Lastly, fold in the chocolate chips. Transfer the mixture to the loaf pan and spread out evenly. Bake for 50-55 minutes or until toothpick comes out clean. Allow to set in the pan for 10 minutes and then transfer to a wire rack to fully cool. Top with flakey sea salt.