Chop cauliflower into small florets, slice onions finely, and dice gherkins evenly.
Combine malt vinegar with mustard powder, turmeric, sugar, and salt. Blend well to ensure all ingredients are incorporated.
Add cornflour to the vinegar mix to thicken the sauce, ensuring it coats the vegetables well.
In a pot, combine the prepared vegetables with the vinegar mix. Stir gently to coat the vegetables evenly.
Gently simmer the mixture to soften the vegetables and allow the flavors to meld together.
Ensure jars are thoroughly cleaned and sterilized to preserve the piccalilli. Heat them in boiling water or an oven.
Once the piccalilli mixture is ready, carefully fill the sterilized jars with the hot mixture.
Seal the jars tightly to preserve the piccalilli for long-term storage.
Allow the piccalilli to age in a cool, dark place for several weeks to intensify the flavors before enjoying.