Make the batter.
Turn on your oven to 350°F (175°C). Prepare a 9×5-inch loaf pan by greasing and flouring it or lining it with parchment paper.
In a big bowl, mix together the mashed bananas, melted butter, and sugar. Mix until everything is well mixed together.
Put the eggs in one by one, and mix well each time you add one. Add the vanilla extract.
In another bowl, mix the flour, baking soda, and salt using a whisk. Slowly mix the powdered ingredients into the mashed bananas until they are just mixed together.
Make a Marble Swirl:
Split the batter into two equal parts. In one part, mix the cocoa powder and milk together until well combined.
Put spoonfuls of the banana and chocolate batter alternately into the loaf pan that has been prepared. Use a knife or stick to gently mix the two mixtures together, making a swirled pattern.
Make the bread.
Put in the oven that has been preheated for 50-60 minutes, or until a toothpick inserted in the middle comes out clean.
Let the bread cool in the pan for 10 minutes before moving it to a wire rack to cool down completely.
Make the caramel topping:
