Preheat your oven to 180c and line two loose bottom cake tins (15cm) with baking paper.
Mix together the milk and vinegar and set aside to allow to thicken.
Combine all of the dry ingredients into a mixing bowl and roughly mix. Add the olive oil and thickened milk mixture, then fold together to create a smooth batter. Finally, stir in your passionfruit.
Divide this between your cake tins and pop into the oven for around 30-35 minutes, or until cooked through. Allow to cool completely on a wire wrack.
To prepare your frosting, beat the butter until light and fluffy, then gradually beat in the icing sugar.
Spread a generous helping of buttercream over one of the cakes and add a layer of passionfruit (one passionfruit) and sandwich the second layer on top.
Garnish with the remaining frosting, passionfruit and fresh berries of your choice.