Whisk all the ingredients together in a heatproof bowl, then place it over a pan of gently simmering water (make sure the bowl doesn't touch the water).
Continue stirring until your curd has thickened. Don’t worry if the curd seems a little runny – it'll thicken up as it cools. http://thewhiterosedentalpractice.co.uk/2017/12 N.B. The mixing is crucial to avoid it curdling or becoming lumpy.
Pour into sterilised jars, seal and keep in the fridge for up to one month.