Beat egg yolks, 4 tablespoons sugar and vanilla in a mixing bowl until thick and creamy.
Pour cream into a saucepan and stir over low heat until it almost comes to the boil. Remove the cream from heat immediately. Stir cream into the egg yolk mixture; beat until combined.
Pour cream mixture into the top of a double boiler. Stir over simmering water until mixture lightly coats the back of a spoon; approximately 3 minutes. Remove mixture from heat immediately and pour into a shallow heat-proof dish.
Bake in preheated oven for 30 minutes. Remove from oven and cool to room temperature. Refrigerate for 1 hour, or overnight. Dish is ready.
If your oven has a grill, you can get a rich, golden brown crust on top of the dish. Preheat the grill.
In a small bowl combine remaining 2 tablespoons caster sugar and brown sugar. Sift this mixture evenly over custard. Place dish under grill until sugar melts, about 2 minutes. Watch carefully so as not to burn.
Remove from heat and allow to cool. Refrigerate until custard is set again.
Try making individual creme brulees for a dinner party. Pour the custard into individual ramekins before baking, but be sure to decrease baking time accordingly.