01 -
Place the finely chopped dark chocolate in a heatproof bowl set over a saucepan of gently simmering water. Stir occasionally until melted and smooth. Remove from heat and allow to cool slightly.
02 -
In a clean bowl, use an electric whisk to beat the egg whites until soft peaks form. Gradually incorporate 75g of caster sugar while whisking, continuing until the mixture is glossy and stiff.
03 -
In a separate bowl, whip the heavy cream until soft peaks form. Refrigerate until required.
04 -
In another bowl, whisk the egg yolks together with the remaining 75g caster sugar until pale and creamy. Slowly whisk in the melted chocolate and hazelnut liqueur to achieve a smooth consistency.
05 -
Gently fold the chilled whipped cream into the chocolate and egg yolk mixture using a spatula. Next, carefully fold in the beaten egg whites, followed by the ground toasted hazelnuts, until evenly incorporated.
06 -
Pour the mousse mixture into a cake ring or springform pan lined with baking paper. Level the surface with a palette knife. Refrigerate for a minimum of 4 hours, ideally overnight, until the mousse is fully set.
07 -
Gently remove the cake from the mould. For presentation, lightly dust the top with cocoa powder or decorate with whole hazelnuts and chocolate shavings. Serve well chilled, accompanied by whipped cream or a drizzle of chocolate sauce if desired.