Put the cream, milk, zest, and cinnamon in a pan and heat gently until it reaches boiling point.
Remove from the heat.
Mix the caster sugar and the cornflour in a bowl.
Stir in the egg yolks until smooth – do not whisk or the mixture will form a froth.
Pour the cream mixture onto the egg mixture, stirring to combine well.
Rinse out the pan and return the mixture to it.
Stir over low heat for 5 minutes until thickened.
Set aside for 30 minutes to infuse and thicken further.
Strain into a large jug and pour it into your serving dishes.
Cover with cling wrap and chill overnight or longer to set
Just before serving – sprinkle some caster sugar evenly over the top of the custards and caramelize quickly with a cooks blowtorch
As the caramel cools, it will harden
Eat within half an hour but do not chill in the refrigerator as this will cause the caramel to soften