I used to live in Spain and that's where I found out about it first.
For 8 portions, you will need:
8 egg yolks
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75g caster sugar extra
1.25 liters of milk
75g corn flour
2 tsp finely grated lemon rind
1 cinnamon stick
1 - Beat yolks and sugar bowl with a balloon whisk, until it gets creamy.
2 - Place 4 liters of of the milk , the ring and the cinnamon in a large saucepan and stir over medium heat until the mixture just comes to the boil. Remove immediately from heat.
3 - Strain milk mixture into a large heatproof jug. Pour the milk texture into the egg texture, whisking constantly. Stir the remaining milk and cornflour in a small jug until smooth and add to egg mixture.
4 - Return the mixture to pan, stirring constantly over heat until mixture boils and thickens.
5 - Pour mixture into a 26cm heatproof pie dish. cover and refrigerate for 4 hours or overnight.
6 - Just before serving, preheat the grill.
7 - Sprinkle the custard with extra sugar place under the grill until sugar is caramelized and serve immediately. Alternatively you can blowtorch it.
Is not suitable for Freezer or Microwave.