125ml lemon juice
zest of 5 lemons
1½ tbsps cornflour
Start by sterilising the jars and lids in boiling water for 5 mins.
Heat all of the ingredients in a pan until the mixture thickens.
Pour the mixture into the jars, filling to just below the rim and screw on the lids.
Put the jars into a large saucepan of boiling water and simmer for 10 minutes to ensure the mixture is sterilised. Remove the jars and cool.