1.Combine chocolate and the cream in a saucepan, stir over a low heat until chocolate is melted and mixture is smooth. Remove from heat and cool to lukewarm.
2.Sprinkle gelatine over 1 tblsp hot water in a cup, whisk briskly with a fork until gelatine is dissolved. Quickly whisk the dissolved gelatine into chocolate mixture.
3.Beat egg whites and vanilla in bowl with electric mixer until soft peaks form, gradually add sugar and continue beating until sugar is dissolved. Fold beaten egg whites through chocolate mixture until combined.
4.Spoon mixture into 4 glasses and refrigerate several hours or overnight until set.
Mousse is best prepared a day ahead. Keep in the refrigerator until required.Note