A creamy and decadently rich chocolate mousse, decorated with whipped cream and cashew nuts. This is perfect for Easter or for a dinner party any time of year, as it is made ahead and chilled overnight.
Put the chocolate in the top of a double boiler (a heat-proof bowl set over a saucepan of simmering water). Add the water and sugar and stir with a wooden spoon over low heat until the chocolate is completely melted and the sugar fully dissolved.
Remove from the heat. Remove the bowl from the hot water. Using a whisk, beat in the egg yolks one at a time, beating well after each addition. Set the chocolate mixture aside to cool for about 15 minutes.
Lightly stir the ground cashew nuts into cooled chocolate mixture.
Put 225ml of the cream and the egg whites in separate clean dry bowls. Whip the cream until to soft peaks. Whisk the egg whites to stiff peaks.
Lightly fold first the cream, then the whisked egg whites into the chocolate mixture. Pour the mixture into a glass serving bowl, cover with cling film and refrigerate overnight or until set.
Just before serving, whip the remaining cream to soft peaks. Pipe rosettes of cream around the edge of the mousse and top each rosette with a cashew nut. Serve.