Ingredients

• 300g (10½ oz) plain chocolate, broken into small pieces
• 200g (7oz) whole blanched hazelnuts
• 150g (5oz) unsalted butter, softened
• 150g (5oz) caster sugar
• 4 medium eggs, separated
• 3tbsp crème fraîche
• Cocoa powder, for dusting
• Chocolate curls, for decorating

Method

1. Melt the chocolate in a bowl over a pan of simmering water. Set aside to cool. Whizz the nuts in a processor until they look like coarse breadcrumbs. Set aside.
2. Beat the butter and sugar until creamy. Add the egg yolks, one at a time, beating as you go. Stir in the melted chocolate, crème fraîche and nuts.
3. Whisk the egg whites until quite firm. Fold into the cake mixture. Tip the mixture into a 20cm (8in) square loose-based tin lined with greaseproof paper and bake at 180°C (350°F, gas mark 4) for 40 mins.
4. Remove the cake from the oven and allow to cool in the tin on a wire rack. Remove from the tin, dust with cocoa powder and decorate with chocolate curls.