Put the milk, zests and cinnamon in a pan and bring to the boil then set aside to infuse for at least 1 hour. When cold and infused, strain through a fine sieve.

Beat the eggs and sugar together until thick and pale and fluffy, then beat in the infused milk and cornflour.

Pour into a clean pan and cook over a low heat for 10 minutes, stirring constantly, until you have a thick custard. Sieve into a jug and pour into eight dishes or large ramekins. Chill in the fridge for at least 3 hours, or overnight, until completely set.

When read to serve, sprinkle a layer of sugar over the top and caramelise quickly with a blowtorch, or under a very hot grill. Chill again for at least an hour before serving.