Begin by making your vegan buttermilk. In a bowl, combine 1 cup of dairy-free milk with 1 tablespoon of apple cider vinegar. Stir and let it sit for about 5-10 minutes.

Sift together 2 cups of self-raising flour, 1 teaspoon of baking powder, and 1 teaspoon of bicarbonate of soda. Set aside.

In a large bowl, whisk together 1 cup of caster sugar, 1/2 cup of sunflower oil, and 1 teaspoon of vanilla extract until smooth. Add in 1 cup of mango purée and mix well. Gradually fold in the dry ingredient mixture and the prepared vegan buttermilk.

Preheat your oven to 180°C (356°F). Divide the batter among three greased and lined 8-inch round cake tins. Bake for 25-30 minutes or until golden brown.

While the cake layers cool, prepare the buttercream. Beat 1 cup of softened dairy-free butter until creamy. Gradually add 3-4 cups of powdered icing sugar and 1/2 cup of mango purée, then whip until light and fluffy, about 3-5 minutes.

Once cooled, assemble the cake by placing one layer on a platter, spreading with buttercream, drizzling with mango purée, and sprinkling with coconut.

Frost the top and sides with the remaining buttercream, pipe decorations, and drizzle with more mango purée.