1. Walnuts must be picked before the shell has hardened. The first week in July is usually the latest time to gather them for pickling.
2. Skin and chop the onions. Boil all the ingredients together, except the walnuts.
3. Wearing gloves to prevent staining your hands, cut up the walnuts, crush them, and put into a large pan or basin.
4. Pour the boiling vinegar over them, and leave for 14 days, stirring daily.
5. Strain off the liquid and simmer it in a pan for about an hour.
6. Pour it into prepared bottles, leaving a headspace, and seal at once.
7. Label when cold. Discard the crushed walnuts.
To sterilise bottles see Sterilising Bottles