Heat oven to 325° F. In a saucepan, warm the cream over low heat just until hot.
In a medium heat-proof bowl, beat yolks, vanilla and sugar together until light. Slowly whisk the warm cream into the egg mixture. Evenly divide the mixture into four 6-ounce ramekins and place ramekins in a baking dish; fill dish with boiling water halfway up the sides of the ramekins. Bake for 30 to 40 minutes, or until centers are barely set. Cool completely. Refrigerate for several hours and up to 2 days.
When ready to serve, top each custard with about a teaspoon of sugar in a thin layer. Place ramekins under a broiler 2 to 3 inches from heat source. Turn on broiler. Cook until sugar melts and caramelizes, about 5 minutes. Chill until ready to serve.