• Preheat your oven to 160°C (fan). Grease and line three 8-inch (20 cm) cake tins with parchment paper to prevent sticking.
  
• Place the dark chocolate and butter into a heatproof bowl set over a pan of gently simmering water. Stir occasionally until melted and smooth, then remove from heat. You can also melt them together in short microwave bursts, stirring between each one.
  225 Grams Dark chocolate, 225 Grams Unsalted Butter
• In a small cup, dissolve the instant coffee granules in 125 ml of boiling water and stir this into the melted chocolate mixture. Set aside to cool slightly.
  1 Tablespoon Instant coffee granules
• In a large mixing bowl, combine the flour, cocoa powder, caster sugar, light brown sugar, baking powder, and bicarbonate of soda. Mix well so the dry ingredients are evenly distributed.
  175 Grams Plain Flour, 25 Grams Cocoa powder, 1 Teaspoon Baking powder, ¼ Teaspoon Bicarbonate of soda, 200 Grams Caster sugar, 200 Grams Light brown sugar
• In another bowl, whisk together the eggs, buttermilk, and orange essence until smooth.
  4 Medium Eggs, 75 Milliliters Buttermilk, 2 Teaspoons Orange essence
• Pour the melted chocolate mixture and the egg mixture into the bowl of dry ingredients. Mix everything together until the batter is smooth and slightly runny with no visible lumps. A stand mixer makes this easy, but a hand whisk or spatula will do the job.
• Divide the batter evenly among the three prepared cake tins. Smooth the tops, then bake for 25-30 minutes or until a skewer inserted into the center comes out clean. If the skewer comes out with wet batter, bake for a few more minutes and test again.
• Once baked, remove the tins from the oven and allow the cakes to cool in their tins for about 10 minutes. Carefully turn them out onto a wire cooling rack and let them cool completely before frosting.

To Make the Buttercream

• In a large bowl or the bowl of a stand mixer, beat the unsalted butter for 1-2 minutes until soft and fluffy.
  450 Grams Unsalted butter
• Gradually add the icing sugar, about one-third at a time, beating well between each addition. The mixture should become light, smooth, and pale.
  900 Grams Icing sugar
• Add the melted Terry's Chocolate Orange and continue beating until fully combined and silky. If your buttercream feels too thick, add a tablespoon of milk to loosen it.
  300 Grams Terry's chocolate orange

To Assemble the Cake

• Place one cooled cake layer onto a serving plate or cake stand. Spread a generous layer of buttercream evenly across the top using an offset spatula or knife.
  
• Add the second cake layer and repeat with another layer of buttercream. Finally, place the third cake layer on top and cover the entire cake with a thin layer of frosting to seal in crumbs. Chill for 15 minutes, then spread or pipe on a second, smooth layer of buttercream.
  
• If you want to decorate further, use a piping bag fitted with a star nozzle to pipe swirls of buttercream around the top edge. Add Terry's Chocolate Orange slices on top and finish with sprinkles if desired.
  Terry's chocolate orange, Sprinkles
  
• Refrigerate the cake for at least 2 hours before slicing to help the buttercream set. Serve at room temperature for the best flavor and texture.