Preheat oven to 160°C Fan/180°C/350°F. Grease and line a 9x5 loaf pan with greaseproof or parchment paper, ensuring the paper hangs over two sides.
Position the rack on the third shelf or in the centre of the oven.
In a large mixing bowl, whisk together the sugar and eggs until well combined.
Mash the bananas with a fork. Add the mashed bananas, buttermilk, vanilla extract, oil and melted butter to the sugar mixture. Mix well to combine.
In a separate medium bowl, sift together the flour, cocoa powder, baking soda, baking powder, and salt.
Gently fold the dry ingredients into the wet mixture until just combined (do not overmix)
Fold in the chocolate chips.
Pour the batter into your prepared loaf pan, smoothing the top. Sprinkle with extra chocolate chips on top if desired.
Bake for about 55 to 60 minutes, or until a toothpick inserted into the centre comes out with only a few moist crumbs.
Leave to cool in the pan on a wire rack for 10 minutes, then lift out using the parchment paper over hang. Allow it to cool completely before slicing and serving.
