Preheat the oven to 350°F / 180°C. Place ¾ cup / 175ml ramekins in a deep roasting pan.
Split 1 vanilla bean. Heat 425ml of heavy cream and 100ml of whole milk with the bean and scraped seeds until bubbles appear at the edge; remove from the heat.
Whisk 5 egg yolks with 50g of superfine sugar for 1 minute, until pale. Slowly whisk in the hot cream. Strain into a large measuring cup and skim off the foam.
Fill the ramekins. Pour hot water into the roasting pan to ⅝in / 1.5cm deep. Lay a baking sheet above the ramekins, leaving a small gap for steam.
Bake for 30-35 minutes, until the centers wobble gently but are softly set. Lift out carefully, cool briefly, then refrigerate until completely cold.
Divide 6 teaspoons of superfine sugar evenly over the custards. Lightly mist with water. Caramelize with a kitchen torch, keeping the flame moving. Let the crust harden before serving.
