- Preheat the oven to 350˚F. Grease and line with parchment an 8 x 5 loaf pan (1lb loaf size).
- In a large bowl, mash the bananas with a fork until as smooth as possible. Its ok if there are a few little lumps of banana left in the mixture. Mix in the water, flax meal, oil and sugar.
- Next sift the flours, baking soda and salt straight into the banana mixture. Fold everything together until the batter is just mixed. Divide the batter equally between 2 medium sized bowls.
- To one half of the batter, add the sifted cocoa powder and chocolate chips, mix well. To the other half of the batter add the peanut butter and mix well.
- Scoop ¼ cup of the chocolate batter and place it in the top right-hand corner of the prepared loaf pan. Take another ¼ cup scoop of chocolate batter and place it in the bottom right-hand corner of the pan and then finally place another ¼ cup scoop in the middle left hand side of the loaf pan. Now take ¼ cup scoops of the peanut butter flavoured batter and place them in the 3 gaps left in the pan. For the next layer repeat the process but dollop the peanut butter batter on top of the chocolate batter and the chocolate batter on top of the peanut batter. This will create the marbled pattern. Repeat these steps until all of the batter is used up. Then take a wooden skewer and make a few swirls in the top of the batter. Sprinkle with a few extra chocolate chips if desired.
- Bake in the centre of the oven for 60 to 70 minutes, until a wooden skewer inserted into the middle of the loaf comes out clean. Once fully cooked, remove from the oven and allow to cool in the pan for 20 minutes, then remove from the pan and transfer to a wire rack to continue cooling.