Make the vanilla custard
Place the cream, egg yolks, potato flour, and sugar in a small saucepan and whisk together (do not use a steel whisk as it can turn the custard grayish). Cook over low heat, stirring constantly, until the custard thickens. Remove from heat and stir in the vanilla. If cooking the custard with potato starch flour you need to use the custard shortly after you make it. If using corn starch the custard can be prepared a day ahead and stored in the refrigerator.