Start by weighing up all your ingredients. separate the yolks from the whites, grate the zest of the lemons and squeeze out the juice.
Mix the cornstarch with a bit of the water and the sugar in a bowl, just enough to make a paste.
ädd the rest of the water to a kettle togeather with the zest of the lemon.
Slowly heat the water until the zest has infused it.
add the lemon juice to the cornstarch and sugar, mix it together and add it to the hot water
continue to heat on medium heat until the mix starts to thicken. Remember to stir continuously not to burn the mix or to get lumps.
When the mix starts to thicken add the butter one spoon at the time
when all the butter is mixed in do the same with the yolks, one at a time.
let the mix boil for one minute on medium heat.
Add a bit of cold water in your sink to let the kettle cool of. This will prevent the afterburn effect.