Zest the lemons into a large microwave friendly bowl add the juice.

Add the butter and caster (superfine) sugar.

Microwave on high for 2 minutes (1100 watts).Then take it out and give it a whisk to mix in the sugar and incorporate the butter. Cool slightly,

Beat the yolks well then add them to the juice mix and whisk well. Put back into the microwave for 30 seconds and whisk repeating the 30 second blasts till the mixture is hot but not boiling. After the second or third whisking you should notice that the mixture is quite thick or starting to get thick and is hot. Strain the mixture through a fine sieve

Now that it is ready pour into sterilized jars ( approx 500 gm ) and refridgerate