Lemon and Lime Curd

4 lemons and 4 limes (zest and juice)

120g butter

450g caster sugar

4 large eggs

Put the zest, juice, butter and sugar in a pan and heat slowly, stirring regularly.  Best the eggs in a bowl.  When the sugar has dissolved fully pour some of the mixture into the eggs and whisk well then return entire mixture to saucepan and stir continuously til boiling.  Keep the mixture boiling for 3 minutes, whisking all the time.  Strain through a sieve to remove zest (optional) then pour into sterilised jars.  Cover and allow to cool before putting in fridge to chill.  Will keep for 3 months in a fridge.