Seven-layered Palermitan chocolate mousse cake is Sicily's most elaborate modern dessert. This stunning mediterranean creation is the ultimate family celebration cake.
Prepare the hazelnut or chocolate sponge: Preheat oven to 350°F. Beat eggs and sugar until thick and pale, then fold in sifted flour and hazelnuts. Bake in a 9-inch pan for 20 minutes until just set. Cool completely before slicing into layers.
Make the dark chocolate mousse: Bloom gelatin powder in 2 tbsp water. Melt dark chocolate with 1 cup cream in a bowl over gentle simmering water. Stir in bloomed gelatin until dissolved. Cool slightly, then fold in half the mascarpone. Chill until barely set.
Prepare the crunchy gianduja layer: Chop toasted hazelnuts and combine with melted milk chocolate and 1 tbsp cocoa powder. Spread thinly on parchment, cool until crisp, then break into pieces.
Assemble layers: Place one sponge layer in a lined 9-inch ring. Brush with espresso. Spread a third of the chocolate mousse, top with crunchy gianduja, another sponge, more mousse, then repeat for all seven layers, finishing with mousse.
Chill and finish: Refrigerate the assembled cake at least 4 hours (preferably overnight) to set all mousse layers. Before serving, dust top with remaining cocoa powder and unmold using a hot knife for clean edges.