Preheat your oven to 175c and line two 16cm loose bottom cake tins with baking paper.
Combine the non-dairy milk and vinegar together and set aside for 5 mins to allow to thicken.
Mix together the dry ingredients (apart from the coffee) in a large mixing bowl.
Add in the mashed banana, olive oil and milk mixture, then fold everything together until smooth.
Divide the mixture into two, and stir the coffee through one half of the batter. Transfer into your cake tins and bake for 35-40 minutes.
Allow the cakes to cool completely. Meanwhile, beat the butter until light and fluffy, then gradually incoorporate the sugar, coffee and cocoa powder. You can add in additional cocoa or icing sugar if you feel your frosting needs to be thicker.
Once cooled, spread a generous layer of frosting over one of the cakes and sandwich together. Cover the cake in the lucious frosting and decorate with fresh fruit or other toppings of choice.