How to make it
9 steps. Take it one step at a time.
Preheat your oven
Preheat your oven to 350°F (177°C). Line six 9-inch (23cm) cake pans with parchment paper or bake in batches.
Beat the 6 egg yolks
Beat the 6 egg yolks with half of the 150g sugar (75g) until pale and thick. In a separate bowl, whisk the 6 egg whites with a pinch of salt until soft peaks form, then gradually add the remaining 75g sugar until stiff peaks form.
10 minFold the egg whites gently
Fold the egg whites gently into the yolk mixture. Sift the 150g cake flour over the batter and fold in, followed by the 40g melted butter.
Divide the batter between the 6 prepared pans
Divide the batter between the 6 prepared pans (approx. 1/2 cup per pan). Bake for 8-10 minutes until golden. Cool completely on a wire rack.
10 minFor the buttercream
For the buttercream: Whisk 4 eggs and 200g sugar in a heatproof bowl over a pot of simmering water. Whisk constantly until the mixture reaches 160°F (71°C) and thickens. Remove from heat and stir in 200g melted dark chocolate. Let cool to room temperature.
15 minBeat the 250g softened butter
Beat the 250g softened butter until creamy, then gradually beat in the cooled chocolate-egg mixture until a smooth, fluffy frosting forms.
5 minAssemble the cake
Assemble the cake by stacking 5 layers, spreading a thin layer of buttercream between each. Use the remaining buttercream to cover the sides and top (except for the 6th layer reserved for caramel). Chill.
For the caramel: Place the 6th sponge layer
For the caramel: Place the 6th sponge layer on a piece of parchment. Melt 150g sugar and 1 tbsp lemon juice in a pan over medium heat until it becomes a golden amber caramel. Immediately pour over the sponge layer and spread evenly with a buttered spatula.
Quickly, before the caramel sets hard, use a well-buttered knife
Quickly, before the caramel sets hard, use a well-buttered knife to mark and then cut the layer into 12 wedges. Once set, arrange these wedges at an angle on top of the frosted cake using dollops of buttercream for support.
A little kitchen wisdom
Ensure the caramel-topped layer is sliced while the sugar is still warm but slightly set using a buttered knife, otherwise, it will shatter. The chocolate buttercream is traditionally made with whole eggs cooked over a double boiler for a silky, stable texture.
