Heat the oven to 170°C. Lightly grease a bread baking tin.
Prepare a flax egg by putting the ground flax seeds in a small bowl, add water and stir. Let sit for about 10 minutes until thick.
Take 3 of the bananas and mash them until smooth.
Add the prepared flax egg and stir again.
Add the coconut sugar, ginger, cinnamon, nutmeg, salt, baking powder and vanilla bean paste and stir well.
Add the self-raising flour and fold in the dough.
Add the oil and combine.
Pour the dough into the baking tin. Take the fourth banana and cut in half lenght-wise. Place on top of the dough cut side up. Sprinkle the porridge oats around the bananas.
Bake for approximately one hour or until you can insert a toothpick in the centre and it comes out clean. Allow cooling completely before cutting into slices.