1. Place the cream in a heat-proof bowl, and set the bowl over a pan of simmering water. Cook until heated through. Using a wire whisk, slowly stir the white chocolate into the warm cream until completely melted. Whisk in the liqueur and vanilla. Cover and chill for 1 hour or until pliable but firm enough to scoop.
2. With 2 teaspoons or a 1 1/4-inch ice cream scoop, make dollops of the chocolate mixture and place on a baking sheet lined with parchment paper. Refrigerate for about 15 minutes, until firm enough to roll into rough spheres.
3. Chill until ready to serve.