Pre-heat your oven to 180c and line a 20x20cm baking tin or dish with baking paper
For the cake; mash the bananas with the back of a fork until smooth. Beat these with the sugar and olive oil.
Combine the oat milk and apple cider vinegar and set aside for 5 minutes.
Place all of the dry ingredients in a separate mixing bowl and toss these through to roughly mix together.
Fold the wet and dry ingredients together to form a smooth batter, including the apple cider vinegar mixture.
Gently stir through the grated courgette and transfer this into your baking dish
Pop this into the oven for 25-30 minutes, then allow to cool on a wire rack.
Meanwhile for the topping; beat the almond butter, cocoa, syrup together, gradually pour in the milk whilst mixing until smooth.
Once the cake has cooled, spread this generously over the top and slice into portions.