Preheat the oven to 320°F/160°C and line a loaf pan with parchment paper.
Peel the bananas, add them to a large bowl and mash them. To the bananas, add the plant-based milk, coconut oil and maple syrup. Give it a quick mix.
Add the flour, baking powder, baking soda, cinnamon powder and a pinch of salt to the wet ingredients and whisk everything together.
Pour about 3/4 of the batter into the loaf pan. With the rest of the batter, add in the cocoa powder, chopped chocolate and 1 teaspoon of plant-based milk. Whisk and pour into the loaf pan. Swirl it around to create the marbled look.
Bake it in the oven for about 1 hour or until golden brown on the top. You can use a wooden stick to test if your banana bread is done in the middle.