Preheat the oven to 180C/160C Fan/Gas 4 and lightly grease a loaf tin with sunflower oil.
Add sunflower oil, eggs, mashed bananas, vanilla extract and almond milk to a large bowl and whisk well.
Add wholemeal flour, cocoa powder, caster sugar, baking soda and salt to another bowl and mix well.
Add flour mix to the egg mix and use a large spoon to mix all the ingredients together until smooth.
Pour the cake batter into the loaf tin and place each half of the sliced banana on top (as pictured). Bake for 50-55 minutes or until a skewer inserted in the center comes out clean.