Preheat oven to 300F (150C).

Beat egg yolks, 4 tablespoons white sugar and the vanilla extract until thick and creamy.

Pour cream into a saucepan and stir over low heat until it almost comes to a boil. Stir the cream into the egg yolk mixture; beat until combined.

Pour the mixture into the top pan of a double boiler. Stir over simmering water until it lightly coats the back of a spoon, about 3 minutes. Pour into a shallow heat-proof dish.

Bake for 30 minutes. Remove and cool to room temperature, then refrigerate at least 1 hour.

Preheat broiler. Combine the remaining sugars and sift evenly over the custard. Place under the broiler until the sugar melts, about 2 minutes.

Remove, cool and refrigerate until set again before serving.