Preheat the oven to 160C. Grease a loaf pan with oil and line it with parchment. My loaf pan measures 7.5 x 3 x 3 inches.
In a wide bowl, take the peeled bananas, mash it well with a fork. To this add brown sugar and oil and mix it well. Keep aside
In another bowl, take flour, baking powder, baking soda and cinnamon powder. Whsik the ingredients well together. Alternatively you can sift the dry ingredients to get a homogeneous flour mix.
Add the flour mix to the banana mix in batches. add water and using a spatula combine it to a batter. Take care while mixing, do not mix vigourously. Use gentle folding.
Add dark chocolate chunks and walnuts to the batter and mix it into the batter. Again use gentle cut and fold method to incorporate it into the batter.
Pour the batter into the prepared loaf pan, bake for 45-50 minutes or until a skewer inserted in the middle comes out clean (check notes)
Once baked, remove the loaf from the oven, let it sit for 10 minutes on the counter. Then using a blunt knife loosen the sides of the loaf from the pan, and slowly unmould it onto a wire rack. Let it cool completely.
Once cool, slice the loaf with a serrated knife and enjoy it warm. Cling wrap the rest of the loaf and it will stay good on the counter for a day.
if storing for more then i would recommend refrigerating it in an air-tight box. While serving from the fridge, microwave the slice for 10-20 seconds and enjoy it warm.