​Method

• zest the lemons and limes then squeeze the juice over the zest

• add the melted butter, egg yolks, sugar, corn flour and whisk

• place in a solid based pan and cook very gently whilst stirring (15 minutes) be careful not to overheat the mixture or it will split

• place immediately in  a sterilized jar, sprinkle top with sugar, allow to cool

• once cold place a lid on and put in the fridge