Preheat your oven to 180c and line two loose bottom cake tins with parchment paper. I've used two 61/2 inch cake tins for this recipe.
In a mixing jug, combine the soy milk and apple cider vinegar and mix together. Set these aside for 5 minutes to allow to thicken and curdle. This will create your vegan buttermilk mixture.
In large mixing bowl, use a wooden spoon to cream together the sugar and olive oil until pale and fluffy. Whisk in the buttermilk mixture.
Sift the dry ingredients, then fold these into the wet ingredients until you're left with a smooth batter.
Stir in your blueberries, then transfer your cake batter into your two cake tins. Bake for 30-35 minutes until beautifully risen and golden. You will know your cake is ready when you can insert a toothpick and this comes out clean.
Allow your cakes to cool completely on a cooling rack whilst you prepare the frosting. To do so, begin by whipping up the butter using an electric hand whisk or stand mixer. Beat the butter until pale and fluffy, then gradually incorporate your icing sugar. Once thick and creamy, add in a few drops of our food colouring/potato powder and continue to mix until you achieve a gorgeous purple hue.
Once your cake has cooled, you can begin to assemble by adding a layer of buttercream over one of the cakes. Add your jam into the centre, then carefully sandwich the second cake layer on top.
Coat your cake in a layer of gorgeous frosting, using a cake scraper to help achieve a really smooth, even finish.
I love you decorate this cake with a generous pile of fresh berries on top and some cute little berry flowers around the side.