6 free-range egg yolks
1 cup caster sugar
1/4 cup cornflour
Finely grated zest of 3 lemons
Juice of 7 lemons (to make 1 1/4 cups of strained juice)
100g butter, chopped
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.
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.