Heat the Milk
In a medium saucepan, gently heat the milk. Add the lemon zest and vanilla sugar. Stir to infuse the flavors.
Whisk Eggs and Sugar
In a bowl, whisk the egg yolks and sugar until pale and fluffy.
Dissolve the Cornstarch
In a separate bowl, mix the cornstarch with 1 tablespoon of cold milk until smooth.
