115g/4oz dark chocolate
4 free-range eggs, separated and at room temperature
70g/2½oz icing sugar
300ml/10 fl oz double cream
Place the chocolate and butter in a large bowl and melt over a pan of simmering water, making sure the bottom of the bowl does not touch the water. Set aside to cool a little.
Add the egg yolks to the chocolate mixture, then stir in the icing sugar.
In a large bowl, whisk the egg whites until they form soft peaks. In a separate bowl, whisk the double cream until soft peaks form when the whisk is removed.
Fold the double cream carefully into the chocolate mixture then fold that mixture into the egg whites.
Pour the mixture into a serving bowl, cover with cling film and transfer to the fridge for a minimum of 12 hours.