Place the milk, lemon zest and 4 dessertspoons of the sugar in a large saucepan and heat slowly.
Meanwhile, in a mixing bowl, beat the egg yolks together with 2 dessertspoons of the remaining sugar and the cornflour until smooth.
When milk is just reaching boiling point, remove from the heat and pour slowly over the egg mixture, stirring constantly. Mix well.
Return mixture to the saucepan and cook slowly for 5 minutes, stirring constantly with a wooden spoon.
Strain into individual ramekins and chill.
Once chilled, sprinkle with the remaining sugar and caramelise with a kitchen blow-torch. Alternatively, preheat the grill to very hot and grill the sugared desserts as close to the heat source as possible until caramelised.