Preheat the oven to 160 °C (315°F/Gas 2–3). Put the cream and vanilla beans in a medium saucepan. Heat together until the cream just begins to boil, then remove the pan from the heat. Whisk the egg yolks, whole egg and sugar together in a stainless steel bowl. While whisking the eggs, slowly pour on the hot vanilla cream. Mix well and then remove the vanilla beans.
Strain the mixture into four 175 ml (5½ fl oz) ceramic ramekins, then place the ramekins in a baking tray of water to form a bain-marie. Put the baking tray in the oven and cook the custard as you would a crème brûlée, for about 30–35 minutes, or until the custard is just set. Remove the custards from the bain-marie and place in the refrigerator for 5–6 hours, or until they are fully chilled and set. Remove the skin from the top before using.