Preheat oven to 350°F (175°C) and grease a loaf pan.
Mash bananas in a bowl until smooth.
Stir in melted butter, sugar, eggs, and vanilla extract.
Whisk together flour, cocoa, baking soda, and salt in another bowl.
Fold dry ingredients into wet ingredients, alternating with espresso.
For the mocha swirl, heat coconut milk until warm, then mix in instant coffee, cocoa, and vanilla.
Pour half the batter into the loaf pan.
Drizzle mocha mixture over it, then add the remaining batter.
Gently swirl with a toothpick for a marbled effect.
Sprinkle chocolate chips on top because why not?
Bake for 50-55 minutes until a toothpick comes out mostly clean.
Cool slightly before slicing, if you have patience.