Preheat your oven to 180c and line your two cake tins with baking paper on the base. Then lightly grease the sides with some non-dairy butter.
In a large mixing bowl, combine your dry ingredients and roughly stir together. Mix together the vinegar, plant milk and olive oil and let this sit for 5 minutes.
Fold the wet and dry mixtures together to create a smooth batter, then divide this between your cake tins.
Place the cakes into the oven to bake for around 30 minutes or until cooked through (check after 25 minutes) and allow to cool on a wire wrack.
For your buttercream frosting, beat the butter until light and fluffy, then gradually stir in the cocoa and icing sugar.
Once your cake has cooled, spread a generous amount of the frosting on one layer and carefully place the second on top. Add the remaining icing to the top layer and garnish with fresh berries for decoration.