The most efficient way to caramelise the sugar layer on top of a creme brulee is scorching it with a small kitchen blowtorch. These are available from speciality kitchenware stores.
750ml (3 cups) pouring cream
1 vanilla bean, split lengthways and seeds scraped
6 egg yolks
75g (⅓ cup) castor sugar, plus 110g (½ cup), extra, to sprinkle
1. Preheat the oven to 160C. Place six 160ml (⅔ cup) heatproof ramekins in a large roasting pan.
2. Put the cream and vanilla seeds in a medium saucepan and bring almost to the boil. Remove from the heat.
3. Use a balloon whisk to whisk the egg yolks and sugar in a large bowl until combined. Whisk in the hot cream mixture until just combined (you don't want it to be frothy). Strain the custard into a jug and divide evenly among the ramekins. Use a tablespoon to remove any air bubbles from the surface of each custard.
4. Add enough boiling water to the roasting pan to reach halfway up the sides of the ramekins. Bake for 20 minutes or until the custards are set, but still a little wobbly in the centre when the ramekins are shaken gently. Transfer the custards to a wire rack and set aside for 15 minutes to cool slightly, then place in the refrigerator, uncovered, for 3 hours or until well chilled.
5. Sprinkle the custards evenly with the extra sugar and use a kitchen blowtorch to caramelise the sugar. Set aside for 5 minutes to allow the caramel to cool and set before serving.
If you don't have a blowtorch, put the extra sugar and 2 tablespoons water in a small heavy-based saucepan over low heat and cook, stirring, for 2 minutes, until the sugar dissolves. Bring to the boil, brushing down the side of the pan often with a pastry brush dipped in water to remove any sugar crystals. Cook, without stirring, for 5 minutes or until the syrup is deep golden.
Remove from the heat and allow the bubbles to subside. Pour evenly over the chilled custards and set aside for 1 minute or until the caramel sets.