Preheat your oven to 350°F and grease a 9x5 loaf pan, then line it with parchment.
Whisk together your banana, vanilla, vinegar, oil, and maple syrup.
Create a well in the center of the bowl and add the flour, cocoa powder, baking soda, baking powder, and salt.
Mix everything together until just combined.
Fold in your chocolate chips, marshmallows, and caramel.
Pour your batter into your loaf pan and spread it out evenly. Top with your marshmallows and press them lightly into the batter.
Bake for 60 minutes, until it's cooked through and a tester comes out clean. You may see melted chocolate on your tester. You're looking to be sure there aren't wet crumbs on your tester, and that the middle is cooked through.
Notes
Recipe adapted from Chocolate Covered Katie. See notes in the post above for tips on choosing ingredients.