In a medium heavy-bottomed pan, heat cream with vanilla beans until bubbles begin to form at edges. Remove from heat and let stand 30 minutes.
Beat egg yolks with sugar until pale and thick. Remove vanilla beans from cream and pour into egg yolk mixture. Cook, without boiling, over low heat until mixture thickens and coats the back of a metal spoon. Remove from heat and divide evenly among 6 large ramekins or custard cups. Cover and refrigerate 3 hours, until set.
Prior to serving, sprinkle remaining sugar evenly over custards and brown with a kitchen torch or under the oven broiler. Refrigerate until serving.