Combine the marshmallow crème, chocolate chips and water in a heavy saucepan over low heat. Cook gently, stirring occasionally until the crème and chocolate are melted and smooth. Remove from heat and let cool. If you cooked it over very low heat, it won’t take long - just about 3 or 4 minutes.
Whip the cream with the vanilla until thick, soft peaks form. Fold the cream into the chocolate mixture until fully combined. Spoon into small dessert dishes and chill for about 5 minutes. Can be made a day ahead.