Ingredients
Method
1.
Put yolks, sugar and cornflour in a medium bowl and stir with a whisk until combined. Stir in lemon zest. Put lemon juice and butter in a medium saucepan over a medium heat. Heat, without boiling, until butter has melted. Remove from heat and gradually pour into egg mixture in a slow steady stream, whisking to combine. Pour mixture back into pan and return to stove over a  medium heat. Cook, stirring constantly with a whisk, for 8 minutes or until mixture is very thick and bubbling.
2.
Transfer to a large bowl, cover directly with plastic wrap and chill for 1 hour or until cold and thick. Store in a jar in fridge for up to 1 week.