five egg yolks
One sugar cup
4 lemons, juiced and zesting
1 stick of cold, cut-up butter
1) Fill a medium saucepan with water until it reaches about an inch over the rim.
2) Over medium-high heat, bring to a simmer.
3) In the meantime, beat the egg yolks and sugar in a medium metal basin for approximately a minute until smooth.
4) Calculate the amount of citrus juice, and if necessary, add just enough cold water to make 1/3 cup.
5) Stir the egg mixture well after adding the juice and zest.
6) As soon as the water comes to a simmer, turn down the heat and set the bowl on top of the pot. (The bowl needs to be big enough to sit above the saucepan without touching the water.
7) Continue whisking for about 8 minutes, or until the mixture is thick and coats the back of a spoon.
8) As soon as the butter has melted, add it to the pan and stir. Remove the pan from the heat immediately.
9) Transfer to a clean container and cover by covering the curd with a piece of plastic wrap.
10) Keep chilled for up to two weeks.