300g unsalted butter
6 whole eggs
9 egg yolks
Juice and zest the lemons and place the juice and zest in a heavy bottomed pan with the sugar, eggs and egg yolks.
Place on a low heat and whisk until the sugar is dissolved.
Slowly whisk in half the butter.
When the butter has melted and the mixture has started to thicken whisk in the remaining butter.
Keep whisking over a low heat until the mixture becomes very thick.
Cool to room temperature and the refrigerate.