Prepare Vegan Buttermilk: Combine 480 ml of dairy-free milk with 2 teaspoons of apple cider vinegar in a bowl. Let sit for 10 minutes to curdle.

Mix Dry Ingredients: Sift together 420 g of self-raising flour, 300 g of caster sugar, 1 teaspoon of baking powder, and 1 teaspoon of bicarbonate of soda in a large bowl.

Combine Wet Ingredients: In another bowl, whisk together the curdled milk, 120 ml of sunflower oil, 1 teaspoon of vanilla extract, and 80 g of mango purée.

Combine Mixtures: Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until just combined.

Bake: Preheat oven to 350°F (175°C) and divide the batter among three prepared 8-inch round cake pans. Bake for 25-30 minutes.

Make Buttercream: Beat 300 g of softened dairy-free butter until creamy, then gradually add 500 g of powdered sugar and 6 tablespoons of mango purée.

Layer Cake: Place one layer on a plate, spread buttercream, drizzle with mango purée, add the second layer, and repeat. Top with the third layer.

Decorate: Coat the outer layer of the cake with remaining buttercream, sprinkle desiccated coconut, and garnish with extra mango purée and fresh mango chunks.