At a glance
You're looking at a stunning hazelnut sponge cake layered with silky caramel cream – about 3 hours total from start to finish. The trickiest part is making the caramel itself: you'll need to watch the heat carefully so it doesn't burn and turn bitter, then whip it with butter and mascarpone for a smooth, luxurious filling. The rest comes down to baking a delicate sponge, cooling it completely, slicing it into layers, and stacking everything together with your caramel cream.
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Tip: batter quantities for a baking sheet
I always use the same sponge recipe and just adjust the ratio of eggs (and other ingredients) to the size of the tin. For one baking sheet: use batter made with 4 eggs for a base sponge layer (the kind used under gelatine-set fillings). For one baking sheet: use batter made with 6 eggs for a sponge that will be sliced and filled.
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Tip: batter quantities for a cake tin
26 cm round cake tin – batter made with 6 eggs. 30 cm round cake tin – batter made with 8 eggs.
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Tip: flavouring the sponge
The sponge can be flavoured with nuts, coconut, almonds, cocoa or chocolate. Whatever ingredient you mix into the flour needs to weigh the same as the eggs you're using. I used 50 g of finely ground hazelnuts in place of 50 g of the fine plain flour.
