Prep the Vegan Buttermilk: In a medium bowl, combine 1 cup of dairy-free milk with 1 tablespoon of apple cider vinegar. Stir gently, then set it aside for about 5-10 minutes.

Make Sponge Batter: In a large mixing bowl, whisk together 2 cups of self-raising flour, 1 cup of caster sugar, 1 teaspoon of baking powder, and 1 teaspoon of bicarbonate of soda. Add 1/2 cup of sunflower oil and 1 tablespoon of vanilla extract. Gradually mix in the prepared vegan buttermilk and 1/2 cup of mango purée until combined.

Bake: Preheat your oven to 180°C (350°F). Grease and line three 8-inch cake pans with parchment paper. Distribute the batter among the pans and bake for 25-30 minutes.

Cool Layers: Remove from the oven and let cool for about 10 minutes before transferring to wire racks to cool completely.

Prepare Buttercream: Beat 1 cup of dairy-free butter until smooth, then add 4 cups of powdered sugar and 1/4 cup of mango purée, blending until fluffy.

Assemble Cake: Start with one sponge layer on a serving plate, spread with mango buttercream, drizzle with mango purée, repeat for second layer, add third layer.

Decorate: Coat with desiccated coconut and pipe decorative swirls of buttercream on top, drizzling with additional mango purée and garnish with fresh mango slices and rosemary if desired.