Preheat your oven to 350°F (175°C). Grease two 8-inch round cake tins and line them with parchment paper for easy removal.

In a large bowl, sift together the flour, cocoa powder, baking soda, and baking powder. Stir in the sugar to combine.

In a separate bowl, whisk together the golden syrup, eggs, sunflower oil, and milk. Gradually pour this into the dry ingredients, mixing until you have a smooth batter.

Divide the batter evenly between the prepared tins. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the tins for 10 minutes before transferring to a wire rack to cool completely.

In a heatproof bowl set over a pot of simmering water, melt the dark chocolate and butter together, stirring occasionally until smooth. Let the frosting cool slightly so it thickens enough to spread.

Place one cake layer on a serving plate and spread a generous amount of frosting on top. Add the second layer and cover the entire cake with the remaining frosting, smoothing it with a spatula for a polished look.

Sprinkle the grated Belgian white and dark chocolate over the top of the cake for a striking finish.