You'll find this classic dessert on menus all over Spain. And with good reason. It's deceptively easy to make, the base is an egg custard, that is chilled rather than baked. A cooks' blowtorch will make the crunchy top perfectly, but a hot grill will work too.
Beat the egg yolks and 150g of the sugar in a bowl until they are really pale and thick. Put 750ml of the milk in a saucepan with the lemon zest and cinnamon stick and bring to a simmer. Remove from the heat and strain it into the eggs, whisking them constantly.
Dissolve the cornflour into the remaining milk and stir into the custard mixture.
Pour this mixture back into the pan and cook on a low heat, stirring constantly, until it just starts to simmer. Remove from the heat and pour into a shallow pudding bowl or into individual dishes. Let the custard cool down then chill in the fridge for an hour.
Before serving, sprinkle the top of the custard with a thin layer of caster sugar then use a cook’s blowtorch to melt the sugar to a golden brown caramel. Leave for a couple of minutes before serving so the sugar sets completely.