Preheat your oven to 180°C (350°F). Lightly grease a 9" x 5" loaf pan and line with parchment paper for easy removal.
In a small bowl, mix the ground flaxseed with water and set aside for 5 minutes to create a flax "egg."
In a large bowl, mash the bananas until smooth. Add the maple syrup, oil, plant-based milk, flax egg, and vanilla extract. Whisk until well combined.
In a separate bowl, whisk together the whole wheat flour, baking powder, baking soda, salt, cinnamon, nutmeg, and raw cane sugar.
Gently fold the dry ingredients into the wet ingredients just until combined. Do not overmix.
If using, fold in the chopped walnuts and chocolate chunks.
Pour the batter into the prepared loaf pan. For an extra touch, place a halved banana on top for decoration.
Bake for 50-55 minutes, or until a toothpick inserted into the center comes out clean. If the top begins to brown too quickly, cover loosely with aluminum foil.
Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing