Ingredients

(Makes 1 large jar. Shelf life 10 days)

4 lemons zest and juice

200g caster sugar

100g butter

4 free range eggs

Method

Put the lemon and grapefruit zest, juice, sugar and butter in a heatproof bowl over a pan of simmering water.

Stir occasionally until the butter has melted.

Then using a whisk, stir in the beaten egg.

Keep gently whisking the mixture over the heat for around 10 mins until thickened like custard.

Pour into sterilised jars – it keeps in the fridge for up to 2 weeks.