Combine 1/3 cup whipping cream and chocolate in medium metal bowl. Set over saucepan of barely simmering water (do not let bottom of bowl touch water). Stir until mixture is smooth. Remove from over water. Cool 15 minutes. Beat remaining 1 2/3 cups whipping cream, sambuca and vanilla in large bowl until soft peaks form. Fold 1/4 of whipped cream into white chocolate mixture to lighten. Fold in remaining whipped cream in 2 additions. Chill topping up to 8 hours.
