Chocolate Sponge

• Preheat the oven to 180°C. Grease two 6-inch baking tins and line the bottoms with parchment paper.
• Whisk eggs and sugar together in a large bowl until pale and fluffy.
• Add vanilla extract and oil to the egg mixture and mix well until fully combined.
• Sift together flour, baking powder, and salt. Fold gently into the wet mixture until smooth. Avoid overmixing, as this can make the sponge dense.
• Dissolve cocoa powder in boiling water and add it gradually to the batter. Mix gently until the batter is uniform and glossy.
• Divide the batter evenly between the two prepared tins. Smooth the tops with a spatula.
• Bake for 30 minutes at 180°C. Check with a toothpick; it should come out clean. Oven temperatures vary, so adjust as needed.
• Let the cakes cool in the tins for 10 minutes, then transfer to a wire rack. Allow to cool completely before layering.

Buttercream

• Whip the butter in a bowl until soft and creamy.
• Gradually add icing sugar while continuing to mix until light in color and fluffy.
• Add cocoa powder and melted dark chocolate chips and mix until smooth and creamy.

Assemble

• Slice each sponge layer in half so you end up with four thin layers. This makes the cake taller and allows for more buttercream between layers.
• Place the first sponge layer on a serving plate. Spread a generous layer of buttercream evenly on top.
• Place the next sponge layer on top and spread more buttercream. Continue until all four layers are stacked.
• Spread the remaining buttercream evenly over the top and sides of the cake. Smooth with a spatula for a clean finish.
• Decorate as desired. You can top with chocolate shavings, chips, or fresh berries. Optionally, drizzle with chocolate ganache for extra indulgence.