For best results, use a high quality white chocolate.
In medium bowl, whip cream until soft peaks form. Chill.
In small bowl, sprinkle gelatin over 1/4 cup cold water. Set aside to soften.
In heat-proof medium bowl or clean top of double boiler, combine sugar and egg whites. Place over pan of simmering water; heat, whisking constantly, until a candy thermometer registers 140 degrees. Remove from heat; whisk until completely cooled and stiff peaks form.
Place gelatin mixture over pan of simmering water; stir to dissolve. Working quickly, stir gelatin into melted white chocolate; then stir in one-third of egg-white mixture. Add chocolate to remaining egg-white mixture. Stir in whipped cream. Chill in airtight container until ready to serve, up to 1 day.